On Nutrition

How do you feel about your metabolism? Too fast? Too slow? Just right? I don’t see too many books and websites offering tips to slow down a fast metabolism, but there’s no shortage of tips on how to boost a “sluggish” metabolism. If you feel like your metabolism needs a kick-start, I have a bit of bad news: Most people have a metabolism within a normal range, and don’t have a lot of control over it. That doesn’t mean that there’s nothing you can do to give your metabolism a healthy nudge.

First, let me clarify what “metabolism” is, and what “sets” it.

Metabolism refers to the processes in your body that burn calories and expend energy. Your base metabolism, or resting metabolic rate (RMR), is the minimum number of calories your body burns just to stay alive, keeping your brain, lungs, blood vessels and every cell in your body running 24/7. The “faster” your metabolism, the more calories you need to maintain your current weight. Genetics are the major determining factor in how fast, or how slow, your metabolism is. Other factors are gender, age, body composition and body size. Why? Because muscle burns more calories than fat, even at rest. In general, men, younger adults and people in larger bodies have more muscle mass than women, older adults and people in smaller bodies.

Who else has more muscle? People who stay physically active — which brings me to the one factor you do have control over.

Exercise increases out daily energy expenditure — slightly — by building more lean tissue, but where we really reap most of the metabolism benefits of more muscle is while we’re actually moving those muscles during exercise.

What about the “afterburn,” that post-exercise boost in your metabolism? It’s a real thing, but it likely depends on how long you exercised, and how intensely. Any type of physical activity that increases your breathing, heart rate and core temperature will give you a temporary metabolism boost, because they shift your body out of “normal” conditions, forcing it to expend extra energy to try to return to normal. Your body would take longer to return to normal after running a marathon than it would if you went for a brisk walk or light jog.

Our RMR slows by 1-2% per decade, but that’s mostly due to muscle loss, not aging itself. The reasons are because of two things that happen in our 30s — our bodies don’t maintain and build muscle as easily, and our activity patterns change due to work, family and social demands. Staying active with aerobic exercise and strength exercise can help counteract “age-related” muscle loss by offsetting the effects of sedentary jobs and leisure activities. Basically: Use it or lose it.

What about food, though?

Claims about metabolism-boosting foods really don’t live up to the hype. For example, catechins in green tea and capsaicin in hot peppers allegedly can boost metabolism, but their effects are very small, and temporary. Protein might be a better bet, simply because it helps maintain muscle. Aim to eat about half your body weight in protein grams each day (if you weigh 150 pounds, that means 75 grams of protein per day), spread across your meals and snacks — but don’t make a point of eating several small meals a day to boost metabolism. It’s true that when you eat, your body burns about 10% of those calories to fuel the effort of digestion. However, that 10% is the same whether your calories are spread over three meals or six.