Experimental research


Thestudy was conducted to investigate how sleep restriction and thesucceeding recovery sleep has an impact on energy usage by sampleexperimentation on healthy Caucasian and African American men andwomen. Since weight gain and obesity is a major societal problem, theexperiment seeks to find out whether race and sleep restriction has akey role in causing them. Laboratory and epidemiological studies haveestablished that the risk factor of obesity and weight gain is aresult of short sleep duration especially in African American men andwomen, although these results show that race is a contributing factorit does not include reduced energy expenditure as a key factor.Moreover, during sleep, the rate of metabolism is low hence if thediet remains the same and the body does not receive enough sleep, itis only logical that there is imbalance in energy utilization.

Ahypothesis is made that the body has a compensory response to theincreased energy intake and employs it to conserve energy during thisstate of imbalance during sleeping hours and wakefulness. Studiessupport this hypothesis while other see that sleep loss will increaserespiratory quotient while others find that it has no actual effect.Recovery sleep is also not included in many studies and where theyare were included they lacked the substantial data to come up withconclusive evidence on the full impact of recovery sleep. Whileconcerning race and gender differences no studies have included thisas a key variable for study. Three authors did the study from theUniversity of Pennsylvania. The first author is Andrea M. Spaeth aPH.D holder and a post doctorate researcher at the school of medicinedepartment. The second author is David F. Dinges a professor ofpsychology in psychiatry department, a PH.D holder who is also thepresident of the sleep research society and chief of division ofdivision in the department of psychiatry. Lastly is Naomi Goel aresearch associate and a professor in psychology in psychiatry. Allthese authors did this study with an objective of assessing theeffects sleep recovery and sleep restriction on energy expenditure inthe racial content of Caucasian and African American men and women.


Thesubject groups under study were healthy adults between the ages of 21to 50 years who were recruited through voluntary participation thatincludes a compensation plan for their involvement. The target groupwas reached through advertisement. Selection was done by use of aquestionnaire the individuals who had no evidence of sleepdisturbances, extreme morningness or habitual napping, throughactigraphy subjects who reported to have 6.5hrs and 8.5hrs habitualnight sleep duration and who go to bed between 2200hrs and 000hrs. Inaddition, the participants were subjected to an interview, physicalexaminations, blood examinations and clinical history to establishwhether they were free from chronic medical and psychologicalconditions. The selected lot did not smoke, work shifts,Trans-meridian travel and did not have irregular sleep and waking uppatterns for a period of 60 days before the study. For the study toobtain accurate data, the subjects were given restrictions on whatnot to take, what is allowable for them to take, and urine screeningwas done a week prior to the laboratory study(Spaeth,Dinges &amp Goel, 2015).

Thestudy used two protocols one experimental and the other conditional.The subjects under study were selected randomly to participate in oneof the two protocols. The protocol that involved experiments was donein the University of Pennsylvania Hospital Chronological laboratorywhere participants were subjected to 14/18 days straight. Clinicaltests were done by use of hospital equipment on a daily basis tocheck vital symptoms and signs. Data collected from both protocolswere used in the study and both protocols consisted of anexperimental condition of two nights with baselines of 10 or 12hours’ time in bed in each night followed with a restriction to 4hours’ time in bed and an additional 12 hours in bed sleep recoveryfor 1 night. The design was aimed to show neurobehavioral deficits inadults while the control conditioning consisted of 10 hours in bed ineach night.

Thesubjects wore a wrist actigraph in the laboratory throughout theprotocol and the subjects were not allowed to exercise and food wasad libitum, caffeine was prohibited while trained staff personnel didthe monitoring. In other protocol days, subjects were givenambulatory electrocardiography and electroencephalography to wear.These experiments were recorded in an interval of 24hours. Lightlevels were also held at a constant of less than 50 lux during thehours that they were awake and less than 1 lux during sleeping hours.Ambient room temperature was held at a constant 22 to 24 degrees.

Metabolicand body composition was measured and data was collected in themorning after an overnight fast, on the fifth night of controlledsleep and the sixth night of restricted sleep. The equipment used tomeasure body composition was by use of a bioelectrical impedanceanalysis while metabolic rate was measured by use of indirectcalorimeter. The results were statistically analyzed by comparison ofsleep variables and demographic between control sleep subjects, sleeprestricted subjects and between sleep restricted subjects ofdifferent gender and racial groups.


Theanalyzed data showed that BMI, age, FFM and percentage of AfricanAmerican men or women difference was not a factor in both sleeprestricted and control subjects and also there was no difference insleep duration between the two. However results show that AfricanAmerican men compared to women they had a higher FFM and were olderin sleep restricted subjects.

Age, y

Weight, kg

BMI, kg m22

Fat-free mass, kg

% Body fat

Pre-study sleep duration

Pre-study sleep midpoint

Control subjects (n 5 11)

34.0 (9.4)

73.4 (11.5)

24.3 (3.4)

52.6 (9.8)

28.3 (10.5)

7h 57m (30.6 m)

03:53 (33.0 m)

Sleep-restricted subjects (n 5 36)

33.8 (9.2)

74.0 (12.3)

24.8 (3.1)

52.2 (11.5)

30.1 (9.4)

7h 55m (26.4 m)

03:41 (43.2 m)

Men (n 5 20)

37.4 (9.5)

79.4 (12.4)

24.7 (3.1)

60.8 (7.8)

23.7 (6.1)

7h 53m (21.6 m)

03:40 (42.6 m)

Women (n 5 16)

29.4 (6.7)

67.2 (8.4)

25.0 (3.3)

41.6 (3.6)

38.1 (6.2)

7h 57m (32.4 m)

03:44 (45.0 m)

Caucasians (n 5 14)

34.1 (7.1)

75.8 (12.4)

25.0 (3.1)

55.0 (12.0)

28.1 (8.8)

7h 53m (24.0 m)

03:50 (37.8 m)

African Americans (n 5 22)

33.7 (10.5)

72.9 (12.4)

24.7 (3.2)

50.5 (11.1)

31.4 (9.8)

7h 56m (28.8 m)

03:35 (46.8 m)

Fig1. Shows the change in body composition amongst all variables understudy.

Betweenday one of sleep restriction to day five, the subjects recorded anincrease in weight of between 1.31± 1.22 kg while in controlsubjects there was no significant change in weight measured frombaseline day one to baseline day five. Even though the difference wasnot significant African American men and women who were sleeprestricted gained more weight than Caucasians from base line day 1 toSR5(Spaeth, Dinges &amp Goel, 2015).

Forbody consumption rate, men consumed more calories than womenthroughout the study did. Resting metabolic rate varied across allthe three variables in sleep-restricted subject but not in controlsubjects. African Americans showed a lower resting metabolic ratethan Caucasians did. On respiratory quotient, Caucasians had a lowerRQ as compared to African Americans during the day and gender had noeffect at all.

Figure2Shows the difference in RMR between African Americans and Caucasians


Thestudy’s findings support the hypothesis because it determined thatif sleep restriction were done on proper conditions, which is limitedcircadian disruptions and performed under ad libitum conditions offeeding, would reduce resting metabolic rate and resting metabolicrate returns to base line levels after a night of sleep recovery. Theresults of this study were conducted in strict regulatory environmentand the experimental design yielding reliable data to come to thisconclusion. As compared to earlier studies that allowed subjects toleave the laboratory and take a walk outside hence leading tocalories consumption and hence a slightly different outcome wasobserved. In practical, this study is used to help African Americanmen and women who report increase in weight that can subsequentlylead to overweight and obesity. The study shows a probable cause andanswer to the cause by advising African American men and women toconsume low calories based type of food than Caucasians do. This isapplicable for African American women who have reports of sleep loss.The study has limitations one of the limitations was the use ofbiomedical impedance analysis. This analysis tool has a limitedsensitivity thereby analyzing changes in body composition was notrelatively accurate and the study was not able to analyze the bodycomposition just after sleep loss. The other limitation was the useof a metabolic cart that was time restricted to the protocol henceonly a 15min duration test was used to analyze metabolic rate. Thecurrent study did not asses’ physical activity since subjects wereconfined in the laboratory vicinity. Lastly, the study did notmonitor extensively women and their menstrual cycle since some weretaking oral contraceptives, this might have influenced the resultsobtained on gender differences. Recommendations are made in that moreextensive research is to be done that incorporates all the aspectsthat limited the above study and to better understand what mechanismis behind the reduced resting metabolic rate that is usually observedin the morning hours.


Spaeth,A. M., Dinges, D. F., &amp Goel, N. (2015). Resting metabolic ratevaries by race and by sleep duration.&nbspObesity,&nbsp23(12),2349-2356.