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How Poor Sleep is Ruining Your Fat Loss Goals


So, you decided to watch that extra show on Netflix or mindlessly scroll through Tik-Tok for a couple hours before getting to bed. Seems harmless, but what you probably didn’t expect would be that your poor sleep hygiene could be significantly effecting your fat loss goals and creating the perfect recipe for not only staying fat; but getting fatter.


"If your goal is to lose fat, skipping sleep is like poking sticks in your bicycle wheels," say’s Plamen Penev, MD, PhD, assistant professor of medicine at the University of Chicago. "Cutting back on sleep, a behavior that is ubiquitous in modern society, appears to compromise efforts to lose fat through dieting.”


In a study performed at University of Chicago by Dr. Penev, a lack of sleep appeared to reduce fat loss by 55 percent. The study followed 10 overweight but healthy volunteers aged 35 to 49 with a body mass index ranging from 25, considered overweight, to 32, considered obese. Participants were placed on an individualized, balanced diet, with calories restricted to 90 percent of what each person needed to maintain his or her weight without exercise.


Each participant was studied twice: once for 14 days in the laboratory with an 8.5-hour period set aside for sleep, and once for 14 days with only 5.5 hours for sleep. They spent their waking hours engaged in home- or office-like work or leisure activities.


The volunteers lost an average of 6.6 pounds during each 14-day session. During weeks with adequate sleep, they lost 3.1 pounds of fat and 3.3 pounds of fat-free body mass, mostly protein. During the short-sleep weeks, participants lost an average of 1.3 pounds of fat and 5.3 pounds of fat-free mass. This means even minimal sleep deprivation can lead to poorer body composition, and a significant loss in muscle mass when dieting.


Getting adequate sleep also helped control the dieters' hunger. Average levels of ghrelin did not change when dieters spent 8.5 hours in bed. When they spent 5.5 hours in bed, their ghrelin levels rose over two weeks from 75 ng/L to 84 ng/L.


Higher ghrelin levels have been shown to "reduce energy expenditure, stimulate hunger and food intake, promote retention of fat, and increase hepatic glucose production to support the availability of fuel to glucose dependent tissues," the authors note. "In our experiment, sleep restriction was accompanied by a similar pattern of increased hunger and … reduced oxidation of fat."

The tightly controlled circumstances of this study may actually have masked some of sleep's benefits for dieters, suggested Penev. Study subjects did not have access to extra calories. This may have helped dieters to "stick with their lower-calorie meal plans despite increased hunger in the presence of sleep restriction," he said. Given the freedom to make decisions in a real-world application, sleep deprivation generally tends to lead dieters to make poor decisions regarding food intake and lean towards highly palatable foods that are high in fat and sugar content. This creates the perfect environment for overeating and weight gain.


The message for people trying to lose weight is clear, Penev said. "For the first time, we have evidence that the amount of sleep makes a big difference on the results of dietary interventions. One should not ignore the way they sleep when going on a diet. Obtaining adequate sleep may enhance the beneficial effects of a diet. Not getting enough sleep could defeat the desired effects."


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