Want to lose weight?
Want to gain muscle?
Things to do:
- Go to the gym. Check.
- Eat more “healthy food” and less unhealthy food. Eat way more healthy food if you want to gain muscle. Check.
- Take some fish oil. Check.
- Sleep more. What?
How could moving less help you lose weight or gain muscle?
Grab your teddy and I’m going to tell you a bedtime story about sleep and metabolism.
Sleep and metabolism
Sleep helps control our metabolism and energy balance. Surprised?
Lack of sleep causes havoc in your body. You get hungrier when you’re tired, because hunger-regulating hormones that tell you to eat go up (ghrelin) and ones that tell you to stop eating go down (leptin) (1).
Lack of sleep also messes up something we all have, called the “hypothalamic-pituitary-adrenal axis”, or HPA for short. It’s not a physical thing like your biceps, but a chain of events that starts at your hypothalamus, an almond-sized part of your brain.
Your hypothalamus is not happy when it hasn’t gotten enough rest and squirts out a bunch of cortico-releasing hormone (CRH) that tells your pituitary gland (another part of your brain) to release — guess what? Corticotropin (aka adrenocorticotropic hormone, ACTH). This tells your adrenals (andrenal cortex) to make a bunch of cortisol. Cortisol does a bunch of things like breaking down protein and increasing blood glucose.
In this week’s review I summarize a study that examines whether more sleep means more fat loss (or whether not enough sleep hinders fat loss) when you’re dieting.
Nedeltcheva AV, Kilkus JM, Imperial J, Schoeller DA, Penev PD. Insufficient sleep undermines dietary efforts to reduce adiposity. Ann Intern Med. 2010 Oct 5;153(7):435-41.
This was a small study: only 10 volunteers (7 men and 3 women) between 35-49 years old, with a BMI between 25-32 kg/m2, on average about 81 kg (179 lb). None had a history of sleep problems.
Why such a small group? One big reason: the volunteers stayed in the lab during the experiment, which involve two 14-day visits. Yup, all the volunteers went to the lab one day and stayed for 14 days. They ate there, they slept there, and they hung out there. Afterwards, the volunteers went off and lived their lives for 3 months, then came back to do it again for a grand total of 28 days in Château d’Lab.
Why two visits? There were two test conditions:
- sleeping 5.5 hours a night; and
- sleeping 8.5 hours a night.
Six volunteers slept 8.5 hours at their first visit and 4 volunteers slept 5.5 hours at their first visit, then they swapped 3 months later.
Before and after their lab stay, the volunteers had 2 days of testing that included measuring weight, body-fat (with DXA, dual x-ray absorption) and 24-hour blood sampling.
Once testing was out of the way the volunteers got a specialized diet that was about 1450 kcal/day — around 2/3 of the calories required for their resting metabolic rate (the rate at which you burn calories while at rest).
During the 14-day diet, the volunteers just hung out inside doing office-type work and recreation, but no exercise. At 1450 kcal/day, you wouldn’t have much energy to do anything anyway.
Since you can’t control exactly how long someone sleeps, the assigned sleep duration of 8.5 or 5.5 hours was actually the time the volunteers had to stay in bed.
Neither group slept the full duration; however, the 8.5 hour group slept over 2 hours longer than the 5.5 hour group.
Sleep and fat loss
Big deal! Two hours of sleep. Sure you feel a little more refreshed, but a red-eye triple shot of caffeine uppers can do the same… or can it?
If you look at total weight lost in the two conditions (Figure 1), there is no difference in weight lost. Both groups lost about 3.0kg (6.6 lb). Quite a bit for 14 days, but you need to remember this was a severe calorie restriction — 1450 kcal/day — and there are consequences.
Figure 3 is a breakdown of how much fat (not weight) was lost and how much fat-free mass (muscle, water, glycogen) was lost in the two conditions.
First thing you notice: both groups lost a lot of fat-free mass (FFM). The 8.5 h lost 1.5 kg and the 5.5 h group lost 2.4 kg of FFM.
Holy! More than half the weight lost was not fat. I guess eating 1450 kcal/day and not exercising tends to cause lean tissue loss. Sure, everybody is happy when they step on the scale. Yay I lost 3 kg in weeks!
Well, that wasn’t fat. In the best scenario (8.5 h) only 1.4 kg was fat and in the worst scenario (5.5 h) only 0.6 kg was fat!
While the fat lost isn’t that great, what’s really interesting was that sleeping more protected fat free mass (i.e. lean tissue – muscle) and led to more fat lost. How easy is that? You can’t use the old excuse “I’m too tired” …to sleep?
Why does sleep matter?
RQ is a ratio of the amount of oxygen versus carbon dioxide a person uses.
It’s easy to measure: all you need to know is how much oxygen and carbon dioxide they’re breathing in and how much they’re breathing out. Calculate the difference and voila.
By knowing the ratio you can estimate whether they are metabolizing more fat, carbohydrate or protein.
Since you never only use one source of energy, it would be a mix of the three, though the higher your RQ the more likely you’re using carbohydrates or protein.
At the end of the study the volunteers who were getting less sleep had lower basal metabolic rates (BMR): 1391 kcal/day compared to 1505 kcal/day in the longer-sleeping group, probably from the loss of fat free tissue. This means that volunteers’ metabolism slowed down more while they were sleep-deprived.
Another important point: they all started with a resting metabolic rate of around 2140 kcal/day. Great, they lost weight, even some fat, but in the process they shot their metabolism. Now when they go back to eating a decent amount of calories, say 2000 kcal/day (below their initial BMR) they will gain weight.
Fasting respiratory quotient (RQ) was higher in the 5.5 h (0.83) compared to the 8.5 h (0.80). Higher RQ means less fat burned (oxidation), but more carbohydrates and likely protein used.
Since the sleep-deprived group lost more fat-free mass they were likely breaking down and using more protein.
There are 3 main findings in this study:
- Eating 1450 kcal/day for 14 days leads to weight loss, about 3 kg; regardless of sleep patterns.
- Sleeping more (7 hours 25 minutes) leads to more fat loss (0.8 kg more) than sleeping less (5 hours 14 minutes).
- Sleeping more reduces loss of fat-free mass (losing 0.9kg less and lower RQ)
- Eating 1450 kcal/day for 14 days messes up your metabolism. After 14 days volunteers’ BMR dropped from 2140 kcal/day to 1391 kcal/day or 1505 kcal/day for the sleep-deprived and rested groups.
If you ever needed a reason to throw out your scale and dump fad dieting, this study is it.
Both conditions lost the same amount of weight, but the rested folks lost 60% more fat compared to the sleep-deprived group. More weight lost does not mean more fat lost.
More sleep means more fat loss, though I’m sure there’s a limit to this, so don’t think you can sleep 20 hours a day and watch the pounds melt away.
Losing a lot of weight quickly is not good. Sleeping a lot can help limit loss of muscle, but severe calorie restrictions less to loss of lean mass and slowing of your metabolism.
Don’t obsess about the scale. Weight lost is not necessarily fat lost.
Don’t obsess about losing weight quickly. Quick weight loss is not quick fat loss — it’s probably water, muscle and carbohydrates (glycogen) and worse, it can severely slow your metabolism.
Sleep at least 7 hours a night. Sleep helps your body deal with the stress of losing weight and limits loss of muscle. Sleeping more while dieting actually help keep your metabolism up.
Eat, move, and live… better.
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