Curious about what factors affect resting metabolic rate (RMR)? RMR is impacted by genetics, age, and sex. For example, men typically have a higher resting metabolic rate than women. Even after adjusting for body composition, age, and activity level, men have a resting metabolic rate that’s 5 to 10% faster than women.
How does age affect resting metabolism? Resting metabolic rate slows by 3 to 5% each decade after the age of 40. This is partially due to a decline in lean body mass. Body surface area plays a role too. Taller people typically have higher resting metabolic rates. Unfortunately, you can’t control your age, sex, genetics, and height. Fortunately, there are factors you can control and many people unknowingly slow their resting metabolic rate and make it harder to control their weight by their dietary and lifestyle habits. How many of these metabolism-slowing mistakes to you make?
Under-eating
Aggressive calorie restriction may help you lose weight in the beginning, at least until your body goes into energy conservation mode. Your body is an adaptation machine and it’s quick to conserve if it senses you’re not supplying it with ample energy. In response to calorie restriction, leptin levels decrease and thyroid hormone levels drop or are converted to an inactive form called reverse T3. This leads to a drop in resting metabolic rate.
Rather than drastically cutting calories, focus on eating cleanly, choosing fiber-rich carbs instead of processed ones. Make sure you’re eating a lean source of protein at every meal. Restricting calories too much will only give you short-term benefits but create long term problems by slowing your metabolism. Don’t try to lose too much too fast.
Not Sleeping Enough
Even one night of too little sleep can slow your metabolism. Combine that with the fact that sleep deprivation escalates levels of hunger-stimulating hormones like ghrelin and you have a sure-fire recipe for weight gain. Lack of sleep also decreases insulin sensitivity so more insulin is floating around in your body to put a damper on fat breakdown. At the same time it increases cortisol levels, a stress hormone that breaks down muscle tissue, boosts visceral abdominal fat and makes you more susceptible to illness due to its effects on immunity. People who don’t sleep enough are also at greater risk for health problems like type 2 diabetes. The take-home message? Make sleep a priority.
Not Resistance Training
We know that we lose muscle mass as we age and this reduces resting metabolic rate. One way to avoid this metabolic slow-down is to do resistance training to maximize metabolically-active lean body mass. In addition, some research shows heavy resistance training increases resting metabolic rate even after you finish doing it. Keep in mind this holds true for high-intensity weight training, not lighter muscle endurance workouts.
Being Too Sedentary When You Aren’t Working Out
Doing a structured workout doesn’t mean you can sit around the rest of the day recovering. Sitting too long is a sure way to send your body into “metabolic hibernation.” When you’re not moving your body expends less energy. Plus, sitting too long alters insulin sensitivity and glucose metabolism and puts you at greater risk for metabolic syndrome.
Sedentary behavior is an independent risk for health problems like type 2 diabetes and heart disease, regardless of whether you exercise for an hour or more a day. Sitting too much is not only bad for your metabolism – it’s bad for your health. Look at it this way. If you get up and walk around for five minutes every hour during an eight hour work day, you’ll burn over 600 additional calories each week. That can have an impact on your weight – and your health.
The solution? Get up and move every 20 minutes even if you only stretch or walk around for a few minutes. Set an alarm on your iPhone or computer as a reminder. It matters when it comes to your metabolism and your health.
Getting Too “Comfy”
The temperature of your environment has an impact on your resting metabolic rate. In a study published in the European Journal of Clinical Nutrition, researchers found energy expenditure was greater at an environmental temperature of 62 degrees Fahrenheit relative to 71 degrees Fahrenheit. Some researchers hypothesize that the fact we live and work in warmer environments partially explains the rise in obesity. Cut back the temperature a bit in your home and you’ll gain a slight metabolic advantage. It’ll save on your heating bill in the winter too.
The Bottom Line?
If you’re making these mistakes that slow down your metabolism, it can make it harder to control your weight. Don’t restrict calories too much, stay active even when you’re not exercising, build more muscle and make sure you’re not skimping on sleep.
References:
J Clin Invest. 1992 Sep;90(3):780-4.
J Appl Physiol. 1994 Jan;76(1):133-7.
European Journal of Clinical Nutrition. April 2002, Volume 56, Number 4, Pages 288-296.
Science Daily. “Lack Of Deep Sleep May Increase Risk Of Type 2 Diabetes”
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