Decoding how the body’s complex chemical processes influence the numbers on your scale
WRITTEN BY Stratton Lawrence
PHOTOGRAPHS BY Scott Henderson
Anyone who’s made a calculated effort to slim down knows the difficulty of subtracting pounds. In theory, losing weight should equate to a basic math formula: use more calories than you consume. Broken down to the fundamentals, it’s quite simple. But simple doesn’t mean easy, thanks to a complicating factor we call metabolism.
Metabolism is the sum of all of the chemical processes occurring within the body and is closely linked with nutrition. Calories are burned through metabolism for three primary purposes. Ten percent of our calorie intake fuels digestion. Another 60 to 80 percent gets used naturally throughout the day, a number known as basal metabolic rate or BMR. (The higher your BMR, the faster and more efficiently your body burns calories.) The remaining 10 to 30 percent of our calories get spent during physical activity. It’s here that we have the most control over our metabolism with an opportunity to flip the calorie input-to-output ratio.
“The entire body is involved in metabolism,” explains Dr. Danielle Metzler, a Roper St. Francis Healthcare affiliated primary care doctor. “It’s the process of how the calories we take in are used at a cellular level.” While diets and supplements often advertise a metabolism boost, Dr. Metzler warns us to be wary of such promises. Tactics like intermittent fasting or drinking green tea may trigger a brief uptick in our metabolic rate, but losing weight—and keeping it off—requires more than just biological hacks. Studies have even shown that quickly losing weight can train the body to lower its BMR, sabotaging our ability to maintain the new weight, even with the same levels of exercise and lower caloric intake.
Is boosting metabolism something we should even try to do? And how can some people consume huge meals without gaining weight, while others struggle to keep off the pounds after a single weekend of splurging? The answers lie in the function of metabolism.
Metabolism’s Genetic Lottery
Like premature hair loss or susceptibility to certain diseases, much of our metabolic lot boils down to genetics. In general, people with a higher percentage of muscle in their body mass have a higher BMR. Muscle cells require more energy to maintain than fat cells. Between two people with the same height and body weight, if one has a higher percentage of muscle, they’ll likely have a higher BMR. (This also means that a genetically male person typically has a higher BMR than a genetically female person).
Genetics aside, age also works against us. During childhood and into our 20s, our bodies need calories to build our organs, muscles and bones, so our BMR is naturally high. “Once we reach our maximum growth, our metabolism slows down,” says Dr. Metzler. From about age 30 on, we each combat an ever-declining BMR.
Despite that, offers Dr. Metzler, it’s a misconception to say that metabolism is solely an innate genetic function. “Sure, everything is built into our genes, but there are things that can be manipulated,” she explains. “While you can’t change your age or height, you can often change your body weight.”
Gaming the System
Age and genetics are limitations, yet many retired people claim to feel their very best in the later stages of life. So what steps can we take now to reach our physical prime? “You absolutely can improve your metabolism,” encourages Dr. Metzler, emphasizing the importance of building muscle mass. “The more muscle you have, the higher your metabolic rate.”
The best way to build muscle is through high-intensity aerobic exercise combined with strength training. That doesn’t have to mean heavy weight lifting—it can be as simple as alternating quick sprints with push-ups or jogging with weights. By increasing muscle, we can elevate our BMR, meaning we’ll burn calories more efficiently throughout the day, even when we’re not working out.
“Any exercise that involves muscle breakdown and muscle building is going to benefit metabolism,” confirms Dr. Metzler. If you’re a daily runner, for example, she suggests cutting that to four days a week and adopting strength-building exercises on the other three.
In addition to building muscle, Dr. Metzler recommends a few additional steps that can help boost BMR:
• Get enough sleep. When we’re tired, our bodies hang on to extra calories as fuel to keep us awake and functioning, rather than burning them off.
• Eat smaller, more frequent meals. Maintaining a steadier glucose level can also stabilize BMR. Focus on lean proteins for muscle building, and avoid refined sugars.
• Stand up. We burn more calories by standing than sitting. If your job requires time at a computer, work standing up whenever possible.
• Stay hydrated. Our cells need water to function, and a steady supply ensures our metabolism doesn’t slow.
• Caffeinate with care. Coffee and tea can cause a short-term spike in our metabolic rate, but long-term dependency may hurt it. For the most benefit, drink an occasional cup of green tea, which contains epigallocatechin gallate (EGCG), a natural substance that promotes our metabolism.
A Better Baseline
Despite the promises of products and plans touting a jolt to our metabolism, there is, unfortunately, no fast way to lasting weight loss. “‘Metabolism boost’ is a buzz phrase that’s a little misleading,” says Dr. Metzler. “It tends to fuel the fire for people who want a quick solution to slimming down or becoming healthier. But even if it’s an extra 10 to 15 pounds, those likely took a few years to put on, and they’ll take years to take off.”
The Biggest Loser helped popularize the idea that people can quickly shed dramatic amounts of weight, but most of that show’s contestants have returned to close their original sizes. That’s because quickly shedding pounds through dramatic caloric deficits (lots of exercise and smaller meals) sends our body into emergency mode and can ultimately lower our BMR.
On the other side of the coin are people with high metabolisms who are underweight or malnourished, and ultimately just as unhealthy as an obese person. Higher metabolism, in and of itself, does not equal good health.
The solution is a marathon, not a sprint. “Adopt a mindset of using the fuel you consume in a mindful, purposeful way, versus mindless eating,” says Dr. Metzler. “If you do aerobic and strength-training exercises and you eat whole foods that are rich in plants and lean protein, you’re going to increase your metabolism.”
If the goal of increasing metabolism is weight loss, Dr. Metzler encourages patients to remember that shedding pounds is 80 percent nutrition and just 20 percent exercise. When you consider that only 10 to 30 percent of our metabolism is used for physical activity, the limited success from an approach focused on burning calories becomes clear.
Fads like the ketogenic diet or intermittent fasting may increase metabolism in the short term and result in weight loss, but for most people, they become another “yo-yo diet,” resulting in weight gain when conditions change. What works for the long haul is mindfulness. “You don’t have to track every calorie you consume, but be aware that the food you’re taking into your body is either medicine or poison,” says Dr. Metzler. “A higher metabolism doesn’t necessarily mean you’re healthier, but combined with mindful caloric intake of unprocessed whole food, it can reap health benefits and do wonders for your weight.”
What’s your resting metabolism?
Your body metabolizes most of its calories by maintaining cellular function—not from physical activity. Your basal metabolic rate is the number of calories you burn throughout the day to keep your lungs working, your blood pumping and your organs functioning properly. Knowing your BMR helps you to determine how many calories you need to maintain your current weight—or to gain or shed pounds.
Calculators are available online to determine your BMR, or use the Harris-Benedict Equation. The calculation is different for men and women:
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