TIME-RESTRICTED FEEDING: AN OVERVIEW OF THE CURRENT RESEARCH AND PRACTICAL APPLICATIONS

Jeff Rothschild, CSCS, M.S. cand. Krista Varady, PhD Pera Jambazian, PhD

About Me • Currently finishing M.S. in Nutritional Science at CSULA • Coach College tennis • Work with personal training clients

Background

Unrestricted kcal intake 24 h unrestricted

kcal

3-12 h feeding

12-21 h fasting

24 h fast

3-12 h feeding

12-21 h fasting

Typi

cal d

iet

• 2/3 of U.S. population overweight or obese • 1/3 of U.S. adults meet criteria for metabolic synd

Intermittent Fasting

48 h unrestricted kcal intake

24 h unrestricted kcal

3-12 h feeding

12-21 h fasting

24 h fast (or ~500 kcal)

3-12 h feeding

12-21 h fasting

Nor

mal

die

t A

DF/

AD

MF

• weight loss •  LDL-C, trigs, BP and visceral fat mass • insulin sensitivity

Time-Restricted Feeding

48 h unrestricted kcal intake

24 h unrestricted kcal

3-12 h feeding

12-21 h fasting

24 h fast

3-12 h feeding

12-21 h fasting

AD

F/A

DM

F TR

F N

orm

al d

iet

Circadian rhythms • Bio-rhythms in the absence of external time cues for ~24h • Reset from environmental changes (light-dark,

temperature and feeding cycles)

Circadian rhythms • Affect food metabolism and energy balance

greater impairment of glucose tolerance than theglobal knockout, as predicted. Islets from bothglobal and pancreas-specific knockouts havenormal insulin content, and influx of calcium inresponse to glucose is intact. However, exocytosisis impaired, suggesting that the clock controls thelatest stage in stimulus-secretion coupling.

Findings in experimental genetic models ofclock-gene ablation may also have implicationsfor understanding emerging evidence that thecircadian system participates in human glucosemetabolism. For instance, in genome-wide associa-tion studies, variation in theMelatonin 1b receptor(MTNR1B) and in Cry2 are both associated withblood glucose concentrations[(52) and reviewed in (53)].MTNR1B, the cognate receptorof the circadian-regulated hor-mone melatonin, is expressedin many metabolic tissues,whereasCry2 encodes a clockrepressor. These findings un-derscore the need to incorpo-rate temporal considerationsat the planning stages in futurestudies to account for circadianvariation. Similarly, temporalconsiderations may aid in anal-ysis of experimental geneticmodels because testing at dif-ferent times and under differentenvironmental light cycles mayuncover unanticipated effects.

Sleep and forced circadianmisalignment: genetic modelsand human studies. Ties be-tween circadian disruption andmetabolic disturbance havegarnered attention, includinglarge cross-sectional samplingof populations subjected toshift work. Extensive studiesalso indicate a correlation be-tween sleep time and bodymass index (BMI). Disruptionin specific phases of sleep maybe connected tometabolic func-tion. Subtle tones sufficient toselectively deprive subjects ofslow-wavesleepwithoutproduc-ing conscious wakefulness weresufficient to impair glucose tol-erance (54). Neuroanatomicstudies also indicate intercon-nections between regions of hypothalamus im-portant in circadian signaling, energetics, andsleep (55, 56). At the molecular level, orexin(also termed hypocretin), originally discoveredas a neuropeptide produced in the feeding-stimulatory neurons of lateral hypothalamus, ispositioned at the intersection of neuronal systemscontrolling sleep, circadian output, andmetabolism(56). Analysis of orexin receptor 2 knockout mice

indicates that lack of orexin signaling increasessusceptibility to obesity (rather than the originalexpectation that orexin, a potent wakefulness-inducing peptide, would induce adiposity) (57).Orexin receptor 2 mutations also account forcanine narcolepsy, and orexin deficiency is ahallmark of the disease in humans (58). Activityof the orexin neuron is modulated by glucose andintegrates signals downstream of leptin-responsiveneurons within the arcuate nucleus. Leptin alsoaffects sleep, possibly independently of effectson body weight, raising the need to further defineleptin actions in this process (59). Manipulationof orexin signaling, an integrator of energetic and

circadian signals, may thus provide opportunitiesto intervene not only in disorders of sleep but alsoin related metabolic complications.

In humans exposed to a light/dark cyclelengthened to 28 hours, out of synchrony with theendogenous clock, the sleep/wake cycle is drivenat 28 hours, whereas the melatonin and body-temperature rhythm free-runs with a ~24-hourperiod (60). Such “forced desynchrony,” a mani-

pulation that is intended to simulate deleteriouseffects of jet lag or shift work, caused impairedglucose tolerance and hypoleptinemia. Whethercircadian disruption might also affect endocrinepancreas insulin secretion, hepatic gluconeogenesis,and glucose disposal in skeletal muscle in humansawaits further study; however, these results empha-size the clinical linkages between circadian functionand metabolic homeostasis.

Coupling and Outputs: How Do Clocks Senseand Respond to Nutrient Signals?Under homeostatic conditions, the clock acts as adriver of metabolic physiology (Fig. 3). However,

with perturbations in either circadian or metabolicsystems, such as forced behavioral misalignmentwith shift work or, conversely, high-fat feeding, avicious cycle ensues in which disruption of meta-bolic pathways damp and lengthen circadian os-cillations (61). The identity of metabolic sensorsthat may act as intermediates in coupling circa-dian cycles with physiologic systems remainsto be identified. For instance, do changes in cell-

Sleep deprivationProlonged wakefulnessHigh-fat diet

PancreasInsulin secretion

FatLipogenesisAdiponectin production

MuscleFatty acid uptakeGlycolytic metabolism

LiverGlycogen synthesisCholesterol synthesisBile acid synthesis

SLEEPFASTING

Insuli

n s

ecretion

Sym

path

etic

tone

Glu

coco

rtico

ids

Growth hormone

Melatonin secretion

Insulin resistanceInsulin secretion

WAKEFEEDING

Leptin secretionGluconeog

enes

is

LiverGluconeogenesisGlycogenolysisMitochondrial biogenesis

MuscleOxidative metabolism

PancreasGlucagon secretion

FatLipid catabolismLeptin secretion

Fig. 3. The clock partitions behavioral and metabolic processes according to time of day. The clock coordinates ap-propriate metabolic responses within peripheral tissues with the light/dark cycle. For example, the liver clock promotesgluconeogenesis and glycogenolysis during the sleep/fasting period, whereas it promotes glycogen and cholesterolsynthesis during the wake/feeding period. Proper functioning of peripheral clocks keeps metabolic processes in synchronywith the environment, which is critical for maintaining health of the organism. Different tissues exhibit distinct clock-controlled properties; thus, ablation of the clock in certain tissues will cause opposing effects on metabolic function asuncovered through dynamic challenges at different times in the cycle under different nutrient conditions. Aging, diet, andenvironmental disruption such as shift work may also affect the integration of circadian and metabolic systems.

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Bass and Takahashi 2010

Circadian rhythms

Bass and Takahashi 2010

greater impairment of glucose tolerance than theglobal knockout, as predicted. Islets from bothglobal and pancreas-specific knockouts havenormal insulin content, and influx of calcium inresponse to glucose is intact. However, exocytosisis impaired, suggesting that the clock controls thelatest stage in stimulus-secretion coupling.

Findings in experimental genetic models ofclock-gene ablation may also have implicationsfor understanding emerging evidence that thecircadian system participates in human glucosemetabolism. For instance, in genome-wide associa-tion studies, variation in theMelatonin 1b receptor(MTNR1B) and in Cry2 are both associated withblood glucose concentrations[(52) and reviewed in (53)].MTNR1B, the cognate receptorof the circadian-regulated hor-mone melatonin, is expressedin many metabolic tissues,whereasCry2 encodes a clockrepressor. These findings un-derscore the need to incorpo-rate temporal considerationsat the planning stages in futurestudies to account for circadianvariation. Similarly, temporalconsiderations may aid in anal-ysis of experimental geneticmodels because testing at dif-ferent times and under differentenvironmental light cycles mayuncover unanticipated effects.

Sleep and forced circadianmisalignment: genetic modelsand human studies. Ties be-tween circadian disruption andmetabolic disturbance havegarnered attention, includinglarge cross-sectional samplingof populations subjected toshift work. Extensive studiesalso indicate a correlation be-tween sleep time and bodymass index (BMI). Disruptionin specific phases of sleep maybe connected tometabolic func-tion. Subtle tones sufficient toselectively deprive subjects ofslow-wavesleepwithoutproduc-ing conscious wakefulness weresufficient to impair glucose tol-erance (54). Neuroanatomicstudies also indicate intercon-nections between regions of hypothalamus im-portant in circadian signaling, energetics, andsleep (55, 56). At the molecular level, orexin(also termed hypocretin), originally discoveredas a neuropeptide produced in the feeding-stimulatory neurons of lateral hypothalamus, ispositioned at the intersection of neuronal systemscontrolling sleep, circadian output, andmetabolism(56). Analysis of orexin receptor 2 knockout mice

indicates that lack of orexin signaling increasessusceptibility to obesity (rather than the originalexpectation that orexin, a potent wakefulness-inducing peptide, would induce adiposity) (57).Orexin receptor 2 mutations also account forcanine narcolepsy, and orexin deficiency is ahallmark of the disease in humans (58). Activityof the orexin neuron is modulated by glucose andintegrates signals downstream of leptin-responsiveneurons within the arcuate nucleus. Leptin alsoaffects sleep, possibly independently of effectson body weight, raising the need to further defineleptin actions in this process (59). Manipulationof orexin signaling, an integrator of energetic and

circadian signals, may thus provide opportunitiesto intervene not only in disorders of sleep but alsoin related metabolic complications.

In humans exposed to a light/dark cyclelengthened to 28 hours, out of synchrony with theendogenous clock, the sleep/wake cycle is drivenat 28 hours, whereas the melatonin and body-temperature rhythm free-runs with a ~24-hourperiod (60). Such “forced desynchrony,” a mani-

pulation that is intended to simulate deleteriouseffects of jet lag or shift work, caused impairedglucose tolerance and hypoleptinemia. Whethercircadian disruption might also affect endocrinepancreas insulin secretion, hepatic gluconeogenesis,and glucose disposal in skeletal muscle in humansawaits further study; however, these results empha-size the clinical linkages between circadian functionand metabolic homeostasis.

Coupling and Outputs: How Do Clocks Senseand Respond to Nutrient Signals?Under homeostatic conditions, the clock acts as adriver of metabolic physiology (Fig. 3). However,

with perturbations in either circadian or metabolicsystems, such as forced behavioral misalignmentwith shift work or, conversely, high-fat feeding, avicious cycle ensues in which disruption of meta-bolic pathways damp and lengthen circadian os-cillations (61). The identity of metabolic sensorsthat may act as intermediates in coupling circa-dian cycles with physiologic systems remainsto be identified. For instance, do changes in cell-

Sleep deprivationProlonged wakefulnessHigh-fat diet

PancreasInsulin secretion

FatLipogenesisAdiponectin production

MuscleFatty acid uptakeGlycolytic metabolism

LiverGlycogen synthesisCholesterol synthesisBile acid synthesis

SLEEPFASTING

Insuli

n s

ecretion

Sym

path

etic

tone

Glu

coco

rtico

ids

Growth hormone

Melatonin secretion

Insulin resistanceInsulin secretion

WAKEFEEDING

Leptin secretionGluconeog

enes

is

LiverGluconeogenesisGlycogenolysisMitochondrial biogenesis

MuscleOxidative metabolism

PancreasGlucagon secretion

FatLipid catabolismLeptin secretion

Fig. 3. The clock partitions behavioral and metabolic processes according to time of day. The clock coordinates ap-propriate metabolic responses within peripheral tissues with the light/dark cycle. For example, the liver clock promotesgluconeogenesis and glycogenolysis during the sleep/fasting period, whereas it promotes glycogen and cholesterolsynthesis during the wake/feeding period. Proper functioning of peripheral clocks keeps metabolic processes in synchronywith the environment, which is critical for maintaining health of the organism. Different tissues exhibit distinct clock-controlled properties; thus, ablation of the clock in certain tissues will cause opposing effects on metabolic function asuncovered through dynamic challenges at different times in the cycle under different nutrient conditions. Aging, diet, andenvironmental disruption such as shift work may also affect the integration of circadian and metabolic systems.

www.sciencemag.org SCIENCE VOL 330 3 DECEMBER 2010 1353

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greater impairment of glucose tolerance than theglobal knockout, as predicted. Islets from bothglobal and pancreas-specific knockouts havenormal insulin content, and influx of calcium inresponse to glucose is intact. However, exocytosisis impaired, suggesting that the clock controls thelatest stage in stimulus-secretion coupling.

Findings in experimental genetic models ofclock-gene ablation may also have implicationsfor understanding emerging evidence that thecircadian system participates in human glucosemetabolism. For instance, in genome-wide associa-tion studies, variation in theMelatonin 1b receptor(MTNR1B) and in Cry2 are both associated withblood glucose concentrations[(52) and reviewed in (53)].MTNR1B, the cognate receptorof the circadian-regulated hor-mone melatonin, is expressedin many metabolic tissues,whereasCry2 encodes a clockrepressor. These findings un-derscore the need to incorpo-rate temporal considerationsat the planning stages in futurestudies to account for circadianvariation. Similarly, temporalconsiderations may aid in anal-ysis of experimental geneticmodels because testing at dif-ferent times and under differentenvironmental light cycles mayuncover unanticipated effects.

Sleep and forced circadianmisalignment: genetic modelsand human studies. Ties be-tween circadian disruption andmetabolic disturbance havegarnered attention, includinglarge cross-sectional samplingof populations subjected toshift work. Extensive studiesalso indicate a correlation be-tween sleep time and bodymass index (BMI). Disruptionin specific phases of sleep maybe connected tometabolic func-tion. Subtle tones sufficient toselectively deprive subjects ofslow-wavesleepwithoutproduc-ing conscious wakefulness weresufficient to impair glucose tol-erance (54). Neuroanatomicstudies also indicate intercon-nections between regions of hypothalamus im-portant in circadian signaling, energetics, andsleep (55, 56). At the molecular level, orexin(also termed hypocretin), originally discoveredas a neuropeptide produced in the feeding-stimulatory neurons of lateral hypothalamus, ispositioned at the intersection of neuronal systemscontrolling sleep, circadian output, andmetabolism(56). Analysis of orexin receptor 2 knockout mice

indicates that lack of orexin signaling increasessusceptibility to obesity (rather than the originalexpectation that orexin, a potent wakefulness-inducing peptide, would induce adiposity) (57).Orexin receptor 2 mutations also account forcanine narcolepsy, and orexin deficiency is ahallmark of the disease in humans (58). Activityof the orexin neuron is modulated by glucose andintegrates signals downstream of leptin-responsiveneurons within the arcuate nucleus. Leptin alsoaffects sleep, possibly independently of effectson body weight, raising the need to further defineleptin actions in this process (59). Manipulationof orexin signaling, an integrator of energetic and

circadian signals, may thus provide opportunitiesto intervene not only in disorders of sleep but alsoin related metabolic complications.

In humans exposed to a light/dark cyclelengthened to 28 hours, out of synchrony with theendogenous clock, the sleep/wake cycle is drivenat 28 hours, whereas the melatonin and body-temperature rhythm free-runs with a ~24-hourperiod (60). Such “forced desynchrony,” a mani-

pulation that is intended to simulate deleteriouseffects of jet lag or shift work, caused impairedglucose tolerance and hypoleptinemia. Whethercircadian disruption might also affect endocrinepancreas insulin secretion, hepatic gluconeogenesis,and glucose disposal in skeletal muscle in humansawaits further study; however, these results empha-size the clinical linkages between circadian functionand metabolic homeostasis.

Coupling and Outputs: How Do Clocks Senseand Respond to Nutrient Signals?Under homeostatic conditions, the clock acts as adriver of metabolic physiology (Fig. 3). However,

with perturbations in either circadian or metabolicsystems, such as forced behavioral misalignmentwith shift work or, conversely, high-fat feeding, avicious cycle ensues in which disruption of meta-bolic pathways damp and lengthen circadian os-cillations (61). The identity of metabolic sensorsthat may act as intermediates in coupling circa-dian cycles with physiologic systems remainsto be identified. For instance, do changes in cell-

Sleep deprivationProlonged wakefulnessHigh-fat diet

PancreasInsulin secretion

FatLipogenesisAdiponectin production

MuscleFatty acid uptakeGlycolytic metabolism

LiverGlycogen synthesisCholesterol synthesisBile acid synthesis

SLEEPFASTING

Insuli

n s

ecretion

Sym

path

etic

tone

Glu

coco

rtico

ids

Growth hormone

Melatonin secretion

Insulin resistanceInsulin secretion

WAKEFEEDING

Leptin secretionGluconeog

enes

is

LiverGluconeogenesisGlycogenolysisMitochondrial biogenesis

MuscleOxidative metabolism

PancreasGlucagon secretion

FatLipid catabolismLeptin secretion

Fig. 3. The clock partitions behavioral and metabolic processes according to time of day. The clock coordinates ap-propriate metabolic responses within peripheral tissues with the light/dark cycle. For example, the liver clock promotesgluconeogenesis and glycogenolysis during the sleep/fasting period, whereas it promotes glycogen and cholesterolsynthesis during the wake/feeding period. Proper functioning of peripheral clocks keeps metabolic processes in synchronywith the environment, which is critical for maintaining health of the organism. Different tissues exhibit distinct clock-controlled properties; thus, ablation of the clock in certain tissues will cause opposing effects on metabolic function asuncovered through dynamic challenges at different times in the cycle under different nutrient conditions. Aging, diet, andenvironmental disruption such as shift work may also affect the integration of circadian and metabolic systems.

www.sciencemag.org SCIENCE VOL 330 3 DECEMBER 2010 1353

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Circadian rhythms

greater impairment of glucose tolerance than theglobal knockout, as predicted. Islets from bothglobal and pancreas-specific knockouts havenormal insulin content, and influx of calcium inresponse to glucose is intact. However, exocytosisis impaired, suggesting that the clock controls thelatest stage in stimulus-secretion coupling.

Findings in experimental genetic models ofclock-gene ablation may also have implicationsfor understanding emerging evidence that thecircadian system participates in human glucosemetabolism. For instance, in genome-wide associa-tion studies, variation in theMelatonin 1b receptor(MTNR1B) and in Cry2 are both associated withblood glucose concentrations[(52) and reviewed in (53)].MTNR1B, the cognate receptorof the circadian-regulated hor-mone melatonin, is expressedin many metabolic tissues,whereasCry2 encodes a clockrepressor. These findings un-derscore the need to incorpo-rate temporal considerationsat the planning stages in futurestudies to account for circadianvariation. Similarly, temporalconsiderations may aid in anal-ysis of experimental geneticmodels because testing at dif-ferent times and under differentenvironmental light cycles mayuncover unanticipated effects.

Sleep and forced circadianmisalignment: genetic modelsand human studies. Ties be-tween circadian disruption andmetabolic disturbance havegarnered attention, includinglarge cross-sectional samplingof populations subjected toshift work. Extensive studiesalso indicate a correlation be-tween sleep time and bodymass index (BMI). Disruptionin specific phases of sleep maybe connected tometabolic func-tion. Subtle tones sufficient toselectively deprive subjects ofslow-wavesleepwithoutproduc-ing conscious wakefulness weresufficient to impair glucose tol-erance (54). Neuroanatomicstudies also indicate intercon-nections between regions of hypothalamus im-portant in circadian signaling, energetics, andsleep (55, 56). At the molecular level, orexin(also termed hypocretin), originally discoveredas a neuropeptide produced in the feeding-stimulatory neurons of lateral hypothalamus, ispositioned at the intersection of neuronal systemscontrolling sleep, circadian output, andmetabolism(56). Analysis of orexin receptor 2 knockout mice

indicates that lack of orexin signaling increasessusceptibility to obesity (rather than the originalexpectation that orexin, a potent wakefulness-inducing peptide, would induce adiposity) (57).Orexin receptor 2 mutations also account forcanine narcolepsy, and orexin deficiency is ahallmark of the disease in humans (58). Activityof the orexin neuron is modulated by glucose andintegrates signals downstream of leptin-responsiveneurons within the arcuate nucleus. Leptin alsoaffects sleep, possibly independently of effectson body weight, raising the need to further defineleptin actions in this process (59). Manipulationof orexin signaling, an integrator of energetic and

circadian signals, may thus provide opportunitiesto intervene not only in disorders of sleep but alsoin related metabolic complications.

In humans exposed to a light/dark cyclelengthened to 28 hours, out of synchrony with theendogenous clock, the sleep/wake cycle is drivenat 28 hours, whereas the melatonin and body-temperature rhythm free-runs with a ~24-hourperiod (60). Such “forced desynchrony,” a mani-

pulation that is intended to simulate deleteriouseffects of jet lag or shift work, caused impairedglucose tolerance and hypoleptinemia. Whethercircadian disruption might also affect endocrinepancreas insulin secretion, hepatic gluconeogenesis,and glucose disposal in skeletal muscle in humansawaits further study; however, these results empha-size the clinical linkages between circadian functionand metabolic homeostasis.

Coupling and Outputs: How Do Clocks Senseand Respond to Nutrient Signals?Under homeostatic conditions, the clock acts as adriver of metabolic physiology (Fig. 3). However,

with perturbations in either circadian or metabolicsystems, such as forced behavioral misalignmentwith shift work or, conversely, high-fat feeding, avicious cycle ensues in which disruption of meta-bolic pathways damp and lengthen circadian os-cillations (61). The identity of metabolic sensorsthat may act as intermediates in coupling circa-dian cycles with physiologic systems remainsto be identified. For instance, do changes in cell-

Sleep deprivationProlonged wakefulnessHigh-fat diet

PancreasInsulin secretion

FatLipogenesisAdiponectin production

MuscleFatty acid uptakeGlycolytic metabolism

LiverGlycogen synthesisCholesterol synthesisBile acid synthesis

SLEEPFASTING

Insuli

n s

ecretion

Sym

path

etic

tone

Glu

coco

rtico

ids

Growth hormone

Melatonin secretion

Insulin resistanceInsulin secretion

WAKEFEEDING

Leptin secretionGluconeog

enes

is

LiverGluconeogenesisGlycogenolysisMitochondrial biogenesis

MuscleOxidative metabolism

PancreasGlucagon secretion

FatLipid catabolismLeptin secretion

Fig. 3. The clock partitions behavioral and metabolic processes according to time of day. The clock coordinates ap-propriate metabolic responses within peripheral tissues with the light/dark cycle. For example, the liver clock promotesgluconeogenesis and glycogenolysis during the sleep/fasting period, whereas it promotes glycogen and cholesterolsynthesis during the wake/feeding period. Proper functioning of peripheral clocks keeps metabolic processes in synchronywith the environment, which is critical for maintaining health of the organism. Different tissues exhibit distinct clock-controlled properties; thus, ablation of the clock in certain tissues will cause opposing effects on metabolic function asuncovered through dynamic challenges at different times in the cycle under different nutrient conditions. Aging, diet, andenvironmental disruption such as shift work may also affect the integration of circadian and metabolic systems.

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Circadian rhythms

Circadian rhythms • External LD cycles cue

the suprachiasmatic nucleus (SCN)

Schibler et al 2003

Circadian rhythms • External LD cycles cue

the suprachiasmatic nucleus (SCN)

•  ‘Master clock’

Schibler et al 2003

Circadian rhythms

•  Feeding cycles do not affect the SCN

•  They can independently entrain circadian clocks in peripheral organs

Discordance…..

Time-restricted feeding windows • Increasingly practiced • Research has yet to be summarized

Objective

• To summarize the current literature on the effects of TRF on body weight and other markers of metabolic disease risk in animals and humans.

Methods • Daily TRF windows of 3-12 h

Methods • Daily TRF windows of 3-12 h • Primary endpoints of body weight and/or biomarkers of metabolic disease risk

Methods • Daily TRF windows of 3-12 h • Primary endpoints of body weight and/or biomarkers of

metabolic disease risk • A minimum of 14 d following a TRF protocol

Methods • Daily TRF windows of 3-12 h • Primary endpoints of body weight and/or biomarkers of

metabolic disease risk • A minimum of 14 d following a TRF protocol

• More than 60 studies on Ramadan were found •  Eight included based on largest sample sizes (n ≥ 32), and

inclusion of four or more relevant parameters

Animal research

Animal research

3-4 h TRF Light phase feeding 16-18 weeks

8-9 h TRF Dark phase feeding 16 weeks

12 h TRFLight vs dark phase Low-fat vs high-fat during dark phase

4-6 weeks16 weeks

Animal research

3-4 h TRF Light phase feeding 16-18 weeks

8-9 h TRF Dark phase feeding 16 weeks

12 h TRFLight vs dark phase Low-fat vs high-fat during dark phase

4-6 weeks16 weeks

Animal research

3-4 h TRF Light phase feeding 16-18 weeks

8-9 h TRF Dark phase feeding 16 weeks

12 h TRFLight vs dark phase Low-fat vs high-fat during dark phase

4-6 weeks16 weeks

•  Mice normally consume 60-80% of their daily caloric intake during the dark-phase

3-4 h TRF window – weight gain •  Body weights were 17-18% lower •  Body weight of mice on TRF-HFD

was 12% lower than AL-LFD in spite of the same energy intake

Sherman et al 2012

3-4 h TRF window

Sherman et al 2011, 2012

• Two studies showing decreases in triglycerides, total cholesterol, TNF-α, IL-6 and NF-kb • Increased insulin sensitivity

TNF-α

IL-6

8 h TRF window • Fed mice a high-fat or normal diet during dark hrs, 16 weeks •  Is a calorie always a calorie???

•  In the context of circadian biology, maybe not

NA = normal chow (13% fat) ad lib NT = normal chow 8 h TRF FA = high fat (61% fat) ad lib FT = high fat 8 h TRF

Hatori et al 2012

8 h TRF window • Differences in body weight

•  TRF-HFD consumed = kcals as AL-HFD but weighed 28% less •  TRF normal diet weighed less than AL though the difference did not

reach statistical significance

NA = normal chow (13% fat) ad lib NT = normal chow 8 h TRF FA = high fat (61% fat) ad lib FT = high fat 8 h TRF Hatori et al 2012

8 h TRF window • Differences in body weight

•  TRF-HFD consumed = kcals as AL-HFD but weighed 28% less •  TRF normal diet weighed less than AL though the difference did not

reach statistical significance

NA = normal chow (13% fat) ad lib NT = normal chow 8 h TRF FA = high fat (61% fat) ad lib FT = high fat 8 h TRF Hatori et al 2012

8 h TRF window •  Total cholesterol

•  49% decrease in TC in mice on TRF-HFD

Hatori et al 2012

8 h TRF window • Glucose tolerance

•  Comparable to the controls

Hatori et al 2012

8 h TRF window •  Inflammatory markers

•  Decreased TNF-α both groups

Hatori et al 2012

12 h TRF window

12 h TRF window – body weight •  Fed mice during 12 h light or dark phase, 5 weeks • Kcals and activity were not different

•  Dark-phase fed weighed 13% less than light-phase fed •  Less visceral fat

Salgado-Delgado et al 2010

12 h TRF window – body weight •  Fed mice during 12 h light or dark phase, 6 weeks • Kcals and activity were not different

•  Dark-phase fed weighed 19% less than light-phase fed

Arble et al 2009

12 h TRF window – body weight • Mice fed a low-fat and high-fat diet during the 12 h dark-

phase only, 16 weeks •  No differences in kcals or activity •  TRF showed decreased weight gain, independent of the diet

Tsai et al 2012

12 h TRF window - glucose

Farooq et al 2006

12 h TRF window - cholesterol

Farooq et al 2006

Summary of animal findings

Summary of animal findings

Intervention Body weight Lipids Glucose Inflammation

3-4 h TRF

8-9 h TRF

12 h TRF

-9 to -18%↓ TC, ↓ LDL, ↓ HDL, ↓ TG

↓ Insulin resistance

↓ Il-6, ↓ TNF-a, ↓ CRP, ↓ NFkb

Ø to -28% ↓ TC↑ Insulin

sensitivity↓ Il-6, ↓ TNF-a

Ø to -19% ↓ TC, ↓ TG ↓ Glucose --

Summary of animal findings

Intervention Body weight Lipids Glucose Inflammation

3-4 h TRF

8-9 h TRF

12 h TRF

-9 to -18%↓ TC, ↓ LDL, ↓ HDL, ↓ TG

↓ Insulin resistance

↓ Il-6, ↓ TNF-a, ↓ CRP, ↓ NFkb

Ø to -28% ↓ TC↑ Insulin

sensitivity↓ Il-6, ↓ TNF-a

Ø to -19% ↓ TC, ↓ TG ↓ Glucose --

Summary of animal findings

Intervention Body weight Lipids Glucose Inflammation

3-4 h TRF

8-9 h TRF

12 h TRF

-9 to -18%↓ TC, ↓ LDL, ↓ HDL, ↓ TG

↓ Insulin resistance

↓ Il-6, ↓ TNF-a, ↓ CRP, ↓ NFkb

Ø to -28% ↓ TC↑ Insulin

sensitivity↓ Il-6, ↓ TNF-a

Ø to -19% ↓ TC, ↓ TG ↓ Glucose --

Summary of animal findings

Intervention Body weight Lipids Glucose Inflammation

3-4 h TRF

8-9 h TRF

12 h TRF

-9 to -18%↓ TC, ↓ LDL, ↓ HDL, ↓ TG

↓ Insulin resistance

↓ Il-6, ↓ TNF-a, ↓ CRP, ↓ NFkb

Ø to -28% ↓ TC↑ Insulin

sensitivity↓ Il-6, ↓ TNF-a

Ø to -19% ↓ TC, ↓ TG ↓ Glucose --

Eating at the physiologically ‘wrong’ time can lead to increased weight gain, visceral fat, blood lipids and inflammation along with decreased glycemic control

Human Research

4 h TRF window •  4h TRF every other day for 15 days in healthy men

•  Subjects were instructed to eat enough to maintain body weight

Halberg et al 2005

4 h TRF window •  4h TRF every other day for 15 days in healthy men

•  Subjects were instructed to eat enough to maintain body weight •  Insulin-mediated whole body glucose uptake rates increased 16% •  Insulin-induced inhibition of lipolysis became more prominent •  No changes in IL-6 or TNF-α

Halberg et al 2005

4 h TRF window • Soeters et al 2009 used the same TRF protocol, also

adjusted energy intake to prevent weight change •  No improvements in peripheral or hepatic insulin sensitivity, or any

changes in insulin-induced suppression of lipolysis

4 h TRF window • Soeters et al 2009 used the same TRF protocol, also

adjusted energy intake to prevent weight change •  However, these participants consumed 40% of their daily energy

intake from liquid meals, which may cause different gastric, pancreatic, and biliary responses than consumption of solid meals

Human Research – Ramadan

Ramadan – weight change • Weight changes have ranged from no differences to 5%

weight loss

Ramadan – weight change

Reference Weight Change

Adlouni et al 1997

Nematy et al 2012

Ziaee et al 2006

Temizhan et al 2000

Fakhrzadeh et al 2003

Ravanshad et al 1999

-3%

-2%

-2%

-5% Men, NC Women

-1.8% Men, NC Women

NC

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Ramadan – blood lipids •  Temizhan et al found women had greater improvements in

lipid values than men, but without weight loss

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Ramadan – blood lipids • Nematy et al used the Framingham risk score to show a

significant improvement (p < 0.001) in 10 years coronary heart disease risk

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Ramadan – blood lipids •  Ziaee et al - LDL, HDL and Ø in TC and TG.

•  TG in overweight and in normal-weight subjects

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Factors to consider with Ramadan studies….

Intake • Total energy intake may affect blood lipid values

• Research has shown decreases, no changes, or even increases in energy intake during Ramadan

Macros • There are contrasting reports of whether people change or do not change their macronutrient intakes during Ramadan fasting

Meal timing • During Ramadan, people eat during the physiologically ‘wrong’ time

greater impairment of glucose tolerance than theglobal knockout, as predicted. Islets from bothglobal and pancreas-specific knockouts havenormal insulin content, and influx of calcium inresponse to glucose is intact. However, exocytosisis impaired, suggesting that the clock controls thelatest stage in stimulus-secretion coupling.

Findings in experimental genetic models ofclock-gene ablation may also have implicationsfor understanding emerging evidence that thecircadian system participates in human glucosemetabolism. For instance, in genome-wide associa-tion studies, variation in theMelatonin 1b receptor(MTNR1B) and in Cry2 are both associated withblood glucose concentrations[(52) and reviewed in (53)].MTNR1B, the cognate receptorof the circadian-regulated hor-mone melatonin, is expressedin many metabolic tissues,whereasCry2 encodes a clockrepressor. These findings un-derscore the need to incorpo-rate temporal considerationsat the planning stages in futurestudies to account for circadianvariation. Similarly, temporalconsiderations may aid in anal-ysis of experimental geneticmodels because testing at dif-ferent times and under differentenvironmental light cycles mayuncover unanticipated effects.

Sleep and forced circadianmisalignment: genetic modelsand human studies. Ties be-tween circadian disruption andmetabolic disturbance havegarnered attention, includinglarge cross-sectional samplingof populations subjected toshift work. Extensive studiesalso indicate a correlation be-tween sleep time and bodymass index (BMI). Disruptionin specific phases of sleep maybe connected tometabolic func-tion. Subtle tones sufficient toselectively deprive subjects ofslow-wavesleepwithoutproduc-ing conscious wakefulness weresufficient to impair glucose tol-erance (54). Neuroanatomicstudies also indicate intercon-nections between regions of hypothalamus im-portant in circadian signaling, energetics, andsleep (55, 56). At the molecular level, orexin(also termed hypocretin), originally discoveredas a neuropeptide produced in the feeding-stimulatory neurons of lateral hypothalamus, ispositioned at the intersection of neuronal systemscontrolling sleep, circadian output, andmetabolism(56). Analysis of orexin receptor 2 knockout mice

indicates that lack of orexin signaling increasessusceptibility to obesity (rather than the originalexpectation that orexin, a potent wakefulness-inducing peptide, would induce adiposity) (57).Orexin receptor 2 mutations also account forcanine narcolepsy, and orexin deficiency is ahallmark of the disease in humans (58). Activityof the orexin neuron is modulated by glucose andintegrates signals downstream of leptin-responsiveneurons within the arcuate nucleus. Leptin alsoaffects sleep, possibly independently of effectson body weight, raising the need to further defineleptin actions in this process (59). Manipulationof orexin signaling, an integrator of energetic and

circadian signals, may thus provide opportunitiesto intervene not only in disorders of sleep but alsoin related metabolic complications.

In humans exposed to a light/dark cyclelengthened to 28 hours, out of synchrony with theendogenous clock, the sleep/wake cycle is drivenat 28 hours, whereas the melatonin and body-temperature rhythm free-runs with a ~24-hourperiod (60). Such “forced desynchrony,” a mani-

pulation that is intended to simulate deleteriouseffects of jet lag or shift work, caused impairedglucose tolerance and hypoleptinemia. Whethercircadian disruption might also affect endocrinepancreas insulin secretion, hepatic gluconeogenesis,and glucose disposal in skeletal muscle in humansawaits further study; however, these results empha-size the clinical linkages between circadian functionand metabolic homeostasis.

Coupling and Outputs: How Do Clocks Senseand Respond to Nutrient Signals?Under homeostatic conditions, the clock acts as adriver of metabolic physiology (Fig. 3). However,

with perturbations in either circadian or metabolicsystems, such as forced behavioral misalignmentwith shift work or, conversely, high-fat feeding, avicious cycle ensues in which disruption of meta-bolic pathways damp and lengthen circadian os-cillations (61). The identity of metabolic sensorsthat may act as intermediates in coupling circa-dian cycles with physiologic systems remainsto be identified. For instance, do changes in cell-

Sleep deprivationProlonged wakefulnessHigh-fat diet

PancreasInsulin secretion

FatLipogenesisAdiponectin production

MuscleFatty acid uptakeGlycolytic metabolism

LiverGlycogen synthesisCholesterol synthesisBile acid synthesis

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n s

ecretion

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tone

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ids

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isLiver

GluconeogenesisGlycogenolysisMitochondrial biogenesis

MuscleOxidative metabolism

PancreasGlucagon secretion

FatLipid catabolismLeptin secretion

Fig. 3. The clock partitions behavioral and metabolic processes according to time of day. The clock coordinates ap-propriate metabolic responses within peripheral tissues with the light/dark cycle. For example, the liver clock promotesgluconeogenesis and glycogenolysis during the sleep/fasting period, whereas it promotes glycogen and cholesterolsynthesis during the wake/feeding period. Proper functioning of peripheral clocks keeps metabolic processes in synchronywith the environment, which is critical for maintaining health of the organism. Different tissues exhibit distinct clock-controlled properties; thus, ablation of the clock in certain tissues will cause opposing effects on metabolic function asuncovered through dynamic challenges at different times in the cycle under different nutrient conditions. Aging, diet, andenvironmental disruption such as shift work may also affect the integration of circadian and metabolic systems.

www.sciencemag.org SCIENCE VOL 330 3 DECEMBER 2010 1353

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Sleep schedule • Sleep patterns are drastically changed to allow for early morning meals, affecting metabolism

Seasonality • Ramadan takes place according to the Islamic calendar,

occurring at a different date each year •  Differences in latitude may lead to fasting times of 8-16 hrs

Lab testing • Some studies have performed blood draws in the morning while others in the late afternoon, possibly affecting results

And finally… • Studies that show disparities with trends reviewed here are few in number and generally have smaller sample sizes of 8-25 people •  This review included studies with sample sizes of 32-91

people

Ramadan – fasting blood glucose

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Ramadan – inflammation •  IL-6 decreased by 55% •  hsCRP decreased 52%

Aksungar et al 2007

Intervention Body weight Lipids Glucose

4 h TRF

8-9 h TRF

10-12 h TRF

-- -- ↑, Ø Insulin sensitivity

Ø to -5% ↓ TC, ↓ LDL, ↑ HDL, ↓ TG ↓ ↑ FBG

-2 to -3% ↓ TC, ↓ LDL, ↑ HDL, ↓ TG ↓ FBG

Summary of human findings

Intervention Body weight Lipids Glucose

4 h TRF

8-9 h TRF

10-12 h TRF

-- -- ↑, Ø Insulin sensitivity

Ø to -5% ↓ TC, ↓ LDL, ↑ HDL, ↓ TG ↓ ↑ FBG

-2 to -3% ↓ TC, ↓ LDL, ↑ HDL, ↓ TG ↓ FBG

Summary of human findings

Conclusion • Eating patterns effect circadian rhythms

Conclusion • Findings from animal and human studies suggest that TRF may be an effective dietary intervention to improve a variety of metabolic risk factors • Plasma lipids •  Fasting glucose and insulin •  Insulin sensitivity •  Inflammatory cytokines

Practical application • 12-15 h daily fasting window

• Can depend on the season

Don’t eat when it’s dark outside

Unrestricted food intake internal discordance

Time-restricted feeding internal harmony

Thank You • AHS, Dr Varady, Dr Jambazian, Dr Omary, Cal State LA,

UIC

Questions