Ever notice that when you are tired, you automatically reach for the junk food?
Maybe you think the sugar and carbs will give you an energy boost. Maybe you just don’t have the energy to fix a healthy meal, much less care that you should.
And so you eat the crap, then feel like crap. It becomes a vicious cycle, with your energy up for a few minutes, them plummeting quickly, leading you to reach for even more junk food.
But maybe what you should be doing, instead, is taking a nap.
A recent study builds on evidence that being tired is linked to overeating, poor food choices and weight gain.
In the study, researchers from the University of Chicago Medical Center show how lack of sleep begins the process, amplifying and extending blood levels of a chemical signal that enhances the joy of eating, particularly the guilty pleasures gained from sweet or salty, high-fat snack foods.
During the study, the sleep-deprived subjects — all young, healthy volunteers — were unable to resist what the researchers called “highly palatable, rewarding snacks,” meaning cookies, candy and chips, even though they had consumed a meal that supplied 90 percent of their daily caloric needs just two hours before.
The effects of sleep loss on appetite were most powerful in the late afternoon and early evening, times when snacking has been linked to weight gain.
“We found that sleep restriction boosts a signal that may increase the hedonic aspect of food intake, the pleasure and satisfaction gained from eating,” said Erin Hanlon, PhD, a research associate in endocrinology, diabetes and metabolism at the University of Chicago. “Sleep restriction seems to augment the endocannabinoid system, the same system targeted by the active ingredient of marijuana, to enhance the desire for food intake.”
The chemical signal is the endocannabinoid 2-arachidonoylglycerol (2-AG). Blood levels of 2-AG are typically low overnight. They slowly rise during the day, peaking in the early afternoon.
When the study subjects were sleep-deprived, however, endocannabinoid levels rose higher and remained elevated through the evening, beyond the typical 12:30 p.m. peak, according to the study’s findings.
During that period, the study subjects reported higher scores for hunger and a stronger desire to eat. When given access to snacks, they ate nearly twice as much fat as when they had slept for eight hours.
“The energy costs of staying awake a few extra hours seem to be modest,” said Hanlon. “One study has reported that each added hour of wakefulness uses about 17 extra calories. That adds up to about 70 calories for the four hours of lost sleep. But, given the opportunity, the subjects in this study more than made up for it by bingeing on snacks, taking in more than 300 extra calories. Over time, that can cause significant weight gain.”
For the study, Hanlon’s research team recruited 14 healthy men and women in their 20s. The researchers monitored their hunger and eating habits in two situations: One four-day stay in the university’s Clinical Research Center during which they spent 8.5 hours in bed each night (averaging 7.5 hours of sleep), and another four-day stay when they spent only 4.5 hours in bed (4.2 hours asleep).
The volunteers ate identical meals three times a day, at 9 a.m., 2 p.m., and 7 p.m. Researchers measured levels of the hormone ghrelin, which boosts appetite, and leptin, which signals fullness, in their blood. Previous studies have linked high ghrelin and low leptin levels to reduced sleep time and increased appetite.
They also measured blood levels of endocannabinoids. After a normal night’s sleep, 2-AG levels were low in the morning. They peaked in the early afternoon, soon after lunchtime, then decreased.
After restricted sleep, however, 2-AG levels rose to levels about 33 percent higher than those seen after normal sleep. They also peaked about 90 minutes later, at 2 p.m., and remained elevated until about 9 p.m.
When their sleep was restricted, the volunteers reported a significant increase in their hunger levels, especially after the second meal of the day, when 2-AG levels were highest.
They also estimated that they could eat much more than they predicted the day after a full night’s sleep, the researchers reported.
After the fourth night of restricted sleep, the volunteers were offered a selection of snack foods. Despite having eaten a large meal less than two hours before being offered the snacks, the volunteers whose sleep had been restricted had trouble limiting their snack consumption. They chose foods that provided 50 percent more calories, including twice the amount of fat, as when they were completing the normal sleep phase, the researchers discovered.
What this tells us, according to Hanlon, is that “if you have a Snickers bar, and you’ve had enough sleep, you can control your natural response. But if you’re sleep deprived, your hedonic drive for certain foods gets stronger, and your ability to resist them may be impaired. So you are more likely to eat it. Do that again and again, and you pack on the pounds.”
The Flip Side
Another study shows that overweight adults who lose weight with a high-protein diet are more likely to sleep better.
“Most research looks at the effects of sleep on diet and weight control, and our research flipped that question to ask what are the effects of weight loss and diet — specifically the amount of protein — on sleep,” said Wayne Campbell, a professor of nutrition science at Purdue University. “We found that while consuming a lower calorie diet with a higher amount of protein, sleep quality improves for middle-age adults. This sleep quality is better compared to those who lost the same amount of weight while consuming a normal amount of protein.”
A pilot study with 14 participants found that eating more protein resulted in better sleep after four weeks of weight loss.
Then, in the main study, 44 overweight or obese people were asked to eat either a normal-protein or a higher-protein weight loss diet. After three weeks of adapting to the diet, the groups consumed either 0.8 or 1.5 kilograms of protein for each kilogram of body weight daily for 16 weeks.
The participants also completed a survey to rate the quality of their sleep every month during the study.
What the researchers found is that those who ate more protein while losing weight reported an improvement in sleep quality after three and four months.
A dietitian designed a diet that met each participant’s daily energy needs and then 750 calories in fats and carbohydrates were trimmed each day while maintaining the protein based on whether they were in the higher- or normal-protein group. The sources of protein used in the two studies included beef, pork, soy, legumes and milk protein.
“This research adds sleep quality to the growing list of positive outcomes of higher-protein intake while losing weight, and those other outcomes include promoting body fat loss, retention of lean body mass and improvements in blood pressure,” Campbell said.
Written by Janice Wood
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