Keeping your metabolism running “full steam ahead” becomes even more important with age. We all want our metabolisms “primed” to burn the maximum number of calories even when we’re sitting around or sleeping. Metabolic rate refers to how much energy, or how many calories, your body burns over a 24- hour period. People with a faster metabolism can eat more without gaining weight, while less fortunate folks with a sluggish metabolism have to be more cognizant of portion sizes.
What Makes Up Your Metabolic Rate?
Your metabolic rate can be defined by three parameters – resting metabolism, thermic effect of food and thermic effect of activity. Thermic effect of activity is how much energy you expend when you’re physically active, while the thermic effect of food is the extra calories your body burns to break down and absorb the food you eat. Yes, even digesting food burns calories with protein-rich foods burning slightly more than carbs or fat.
Thermic effect of activity and thermic effect of food only accounts for 30% and 10% of your metabolic rate respective. Resting metabolic rate, which makes up the other 60% of your total energy expenditure is how much energy you expend when you’re not exercising and haven’t just eaten. It includes calories burned when you’re not engaged in an activity and haven’t just eaten a meal, for example, when you’re relaxed in a chair or sleeping. Your body is constantly carrying out tasks that require energy even when you’re not moving.
Have you ever wondered how much your metabolism slows down when you’re sleeping? After all, if you’re getting enough ZZZs, as you should be, you spend almost a third of a 24-hour day sleeping. Here’s news you might not like: Your metabolism slows by 10% during the hours you’re sleeping. Here’s some news you WILL like: Getting enough sleep works in your favor when you’re trying to build a firm, lean, toned physique.
Sleep is Important for Muscle Repair
It’s the periods of rest and sleep between workouts where muscle protein synthesis quietly takes place to help your tissues and muscles repair and grow. In essence, sleep is an “anabolic” phenomenon since it promotes muscle recovery and protein synthesis. During sleep, growth hormone is released, setting the stage for muscle development. In turn, research shows lack of sleep turns on catabolic pathways that degrade muscle tissue, likely due to the effects of increased cortisol released in response to too little sleep.
Another reason you don’t want to skimp on sleep: You need a siesta for brain recovery too. Will you be as motivated to eke out that last super-tough rep on your next workout when you haven’t slept enough? Probably not. Sleep time is time to recover and rebuild, both of which are critical for muscle growth.
Sleep, Metabolism and Weight Control
Despite the slow-down in metabolism, you experience during deep, restful sleep, sleeping enough can help you avoid weight gain. Research shows folks who sleep less than 6 hours a night are almost a third more likely to develop obesity relative to those who sleep longer, around 8 hours. When you don’t snooze enough, the lining of your stomach ramps up production of ghrelin, an appetite hormone that sends your appetite into overdrive – think big time cravings for carby foods. The take-home message? Stay up late and skimp on sleep and you’re more likely to make the wrong dietary choices the next day.
What about Eating Before Bedtime?
You may have heard it’s not smart to eat before bedtime, that you’re more likely to store the calories you eat as fat since your metabolism slows when you’re sleeping. Is there any truth to this? While some research in mice suggests eating before bed makes it harder to control weight, a more recent study involving rhesus monkeys, a more human-like model, dispelled this notion. It showed that monkeys consuming most of their calories at night were not more prone to weight gain. On the other hand, if you’re staying up late AND snacking, you’re disturbing your body’s natural circadian rhythms by eating when you should be sleeping, and this could lead to weight gain.
It also comes down to how much you eat before you go to bed. Some people backload their calories, starving themselves at breakfast and lunch and stuffing themselves in the evening to make up for it. This kind of eating schedule where you’re gorging at night is more likely to lead to weight gain than having a light snack before turning in at night. One study showed people who munch at night (after 8:00 P.M.) typically eat more food, as much as 248 calories more, based on this study.
Does Eating a Snack Before Bed Have Benefits?
If you’re resistance training and trying to build muscle, a snack before bedtime may work in your favor. A study showed consuming protein before bedtime and eating adequate carbs during the day helps your body maintain a positive protein balance. During sleep, when you’re fasting, your body turns to protein from the breakdown of muscle tissue as a fuel source when your glycogen stores and blood glucose level fall. A low-glycemic bedtime snack may help keep your body out of a catabolic state, so you preserve your lean body mass.
The Bottom Line
Your metabolism slows by about 10% during sleep, but lots of good things are happening while you slumber that helps you build lean body mass and keep your weight under control. It’s clear that not sleeping enough puts you at greater risk for a number of health problems, obesity being one of them. Make sure you’re giving your body the downtime it needs to help you stay lean and healthy.
References:
Med Hypotheses. 2011 Aug;77(2):220-2. doi: 10.1016/j.mehy.2011.04.017. Epub 2011 May 7.
Med Sci Sports Exerc. 2012 Aug;44(8):1560-9. doi: 10.1249/MSS.0b013e31824cc363.
WebMD. “10 Things to Hate about Sleep Loss”
Science Daily. “Scientists Dispel Late-Night Eating/Weight Gain Myth” February 2, 2006.
Related Articles By Cathe:
Is Muscle Loss the Only Reason Your Metabolism Slows with Age?
5 Factors that Contribute to a Fast or Slow Metabolism
Metabolic Aging: How Key Hormones Are Affected by Aging
