Have you been training consistently, eating right, but aren’t losing body fat?
It’s quite possible that lack of sleep is sabotaging your fat loss efforts. This might surprise you since many people advertise their lack of sleep as a badge of honor. However, emerging research shows that sleep deprivation leads to behaviors that harm metabolism and undermine fat loss.
A fascinating new study illustrates how lack of sufficient sleep compromises even the best fat loss efforts. Researchers from the University of Chicago put overweight volunteers onto a calorie restricted diet for two weeks and then had them sleep either a “normal” 8.5 hours a night or a “short” 5.5 hour night. In addition to measuring body composition changes, researchers also tested metabolic hormones such as epinephrine, ghrelin, and leptin, and monitored any differences in fat burning between the groups.
The diets supplied 90 percent of calories required to sustain resting metabolic rate, with an average intake of 1,450 calories a day. The diets were 48 percent carbohydrate, 34 percent fat, and 18 percent protein. Results showed that both groups lost roughly the same amount of weight, decreasing body mass by 3 kg. However, the “normal” sleep group lost significantly more body fat, whereas the “short” sleep group had most of their weight loss come from muscle.
Lack of sleep decreased the fraction of weight lost as body fat by an incredible 55 percent:
The “normal” sleep group lost 1.4 kg of fat but the “short” sleep group lost only 0.6 kg of fat, while also losing 2.4 kg of lean mass. This unfavorable change in body composition sets the stage for rebound weight gain because lean mass drives the metabolism and plays a role in strength and the subjects’ ability to move with ease.
Additionally, the “short” sleep group had higher levels of ghrelin (a hormone associated with increased appetite) and lower levels of fat burning as measured by the respiratory exchange quotient. Levels of epinephrine, a hormone involved in fat burning and energy expenditure were also lower, in the “short” sleep group.
Researchers note that parts of the brain require glucose for energy. They theorize that lack of sleep leads the body to shift from burning fat to burning lean mass to supply glucose for the brain during extended wakefulness. Lack of sufficient sleep may compromise the efficacy of typical dietary interventions for weight loss and related metabolic risk reduction.
Another important factor is how our behaviors often change when we are sleep deprived:
Studies show that lack of sleep increases stimulates food intake for “hedonistic” unhealthy foods, particularly those high in carbs, fat, and sodium. For example, one study found that sleep impairment led subjects to eat 300 more calories a day, mostly from junk food.
Lack of sleep also makes people lazy. Not only are you more likely to skip your workout, but research shows people who are sleep deprived lower non-exercise energy expenditure, reducing the amount of calories they burn daily.
Hormone balance is altered, with levels of the stress hormone cortisol going up and insulin sensitivity going down. In men, testosterone is reduced, and both sexes suffer from a decrease in growth hormone (a powerful fat burning hormone) release since you experience the bulk of growth hormone release during sleep.
Mental fatigue leads to an increase in risk taking and makes it harder for us to make good choices, particularly in relation to food. When the stress hormone cortisol is elevated, rational parts of the brain are “turned off” and inhibitions are lower, so we are more likely to justify unhealthy foods or overeating.
If you are trying to lose body fat, fixing your sleep situation should be at the top of your list. Instead of undermining yourself by burning the candle at both ends, set yourself up for success once you start dieting and exercising.
On nights when sleep is restricted, be aware of your eating and activity the following day. Be careful to monitor portions and make healthy food choices, while ensuring you maintain your physical activity levels with a good workout and by getting your steps in.