Because I have so much free time on my hands (hah!), I volunteered (in addition to my 16 credit school course load, husband, and 3 children to try to keep alive) to review a brand new online UW Sports Nutrition course. Did I mention that I have to review about 15 hours of lessons and notes in the next week?! (Picture me: hand smacking forehead). But, it’s been a blast so far, and I thought I’d share some of the fun stuff I’ve been learning and reviewing with you.
We hear a lot in the popular media about “our metabolism” and how certain foods or supplements may (however, most likely not) increase our metabolism. Let’s talk about this a little, but first, what does “METABOLISM” mean, anyway?
Some definitions. Resting metabolism = the energy required (and burned) by your body to (a) stay alive and (b) do all it’s normal stuff, like grow, repair cells, digest your food, breathe, etc. In terms of what your body uses for energy each day or the number of calories you burn (total energy expenditure or TEE), it’s a combination of this resting metabolism rate (RMR) + energy required to digest food (called the “thermic effect of food,” estimated at about 10% of the calorie content of your daily food consumed) + your physical activity levels. Clearly, there is some room to increase the latter (e.g. going from walking to running, taking the stairs instead of the elevator, standing instead of sitting while you work, etc.), in order to increase caloric burn, but interestingly, there are things you can do to affect your RMR as well.
Your RMR is somewhat genetically programmed, and varies according to gender, age, height, genetics, and even potentially, ethnicity. Hormones can affect this rate – both speeding it up or slowing it down. This can be especially true in the case of thyroid hormone, which can have a really drastic effect on your metabolism (and your health) if it’s not closely regulated. Sadly, as we get older, our RMR also decreases slightly – maybe 1-2% each decade. This means that your body slows down and likes to “hold on” to calories (and yes, fat) a lot more.
RMR also changes when you move to a different altitude. For example, you might burn 15-25% more calories at 10,000 feet than you would at sea level. However, RMR adjusts when you return to sea level. Another thing that can affect RMR in the longer term is starvation dieting and chronic dieting. Your body likes to closely regulate its systems – and if you cut calories dramatically, the body reacts by slowing things down dramatically to try to preserve the energy it does have/receive for important things – you know, like your heart beating, breathing, etc. Studies have shown that even after returning to a normal diet, your RMR may not return to its pre-diet state (sometimes 10-25% less than normal). This means that not only will you likely not lose weight, you may actually gain weight. So please, no crash diets, no sudden and dramatic caloric cuts, etc. If you are trying to lose weight, do it gradually, cutting daily caloric intake perhaps 10-20% at a time each week until you hit a reasonable point (typically, not less than 1500 for men or 1200 for women daily).
Interestingly, you CAN increase your metabolism (RMR) on a more permanent basis by increasing your muscle mass (and correspondingly, decreasing your body’s fat mass). This means that even as you get older, you can continue to burn calories efficiently and maintain a normal, comfortable weight by increasing muscle mass through strength training or weight-bearing exercise such as weight lifting, yoga, etc. Studies also indicate (but aren’t entirely conclusive) that exercise, especially interval-type or high-intensity-interval-training (HIIT) may increase metabolism in the longer term as well. Some studies have shown that your metabolism is cranked up for 24-48 hours after an intense interval workout, meaning you burn more calories.
So, time to get your metabolism moving. Lift, run, stretch, sprint, jump and work HARD! And please, HAVE FUN while doing it.