Getting enough sleep gives better diet results
Your fat percentage is too high; you reduce your calorie intake and you hope and pray that you retain lean body mass and lose as much fat as possible. According to researchers at the University of Chicago, the success of this strategy depends on the number of hours you sleep each day.
Sleep, calories & body composition
The link between obesity and sleep is nothing new. Epidemiological studies have shown that people who sleep little put on weight twice as fast as people who get eight hours' sleep a night, [Am J Epidemiol. 2006 Nov 15;164(10):947-54.] and small studies have shown that for every hour of sleep you get in a period of 24 hours your fat percentage is three percent lower.
Lack of sleep stimulates appetite. Not getting enough shuteye lowers the production of appetite suppressant hormones such as leptin, and it stimulates the production of appetite boosting hormones such as ghrelin.
Don't underestimate the effect of lack of sleep on energy intake. In 2010 French researchers published the results of an experiment in which they let students sleep in a laboratory for about four hours a night. [Am J Clin Nutr. 2010 Jun; 91(6): 1550-9.] As a result of the lack of sleep the students spontaneously ate 560 kcal more than they would have eaten after eight hours of sleep a night. That would mean that in less than two weeks the students could have gained a kilogram of fat.
The Chicago research shows that it's not just an unhealthily large appetite that affects dieters with a sleep deficiency. The researchers did a small experiment with ten slightly overweight adults. The subjects followed a diet twice in a laboratory where the researchers were able to control the amount the subjects ate.
During their two-week stay in the lab the subjects were given ninety percent of the kilocalories they would burn if they got no exercise. On one occasion the subjects were allowed to sleep for 8.5 hours a night [open circles] and on the other occasion they were allowed to sleep for 5.5 hours [black circles].
At the end of each of the two-week periods the subjects had lost the same amount of weight, the researchers discovered. But there were statistically significant differences in the effect on the subjects' body composition. When the subjects were only allowed to sleep for 5.5 hours, they lost 55 percent less fat mass and 60 percent more lean body mass.
The combination of a calorie-reduced diet and too little sleep [TIB-5.5h] boosts levels of the appetite hormone ghrelin and lowers the level of the pep hormone nor-epinephrine.
The latter effect may explain the figure above. The respiratory quotient [RQ] is higher in the subjects when they have too little sleep [black circles] than when they get enough sleep [open circles]. That means that a shortage of sleep reduces the amount of fat that the body burns.
"These results highlight the importance of human sleep for the maintenance of fat-free body mass during periods of reduced energy intake and raise the possibility that insufficient sleep may compromise multiple factors that contribute to the efficacy of and adherence to dietary energy-restriction strategies for metabolic risk reduction", write the researchers.
Ann Intern Med. 2010 Oct 5;153(7):435-41.
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