Why can one person eat like a growing teenager and not gain a pound, while another person's every indulgence shows up on the scale? Chalk it up to individual differences in metabolism, muscle mass and physical activity. Metabolism is the process by which our bodies convert what we eat into the energy we need to survive and function. It powers everything from breathing to blinking. A fast metabolism is like a hot furnace that burns through fuel (calories) quickly. A slow metabolism needs less fuel to keep a body running.
It's tempting to throw up our hands and blame weight issues on a slow metabolism, but there are ways to support metabolism and maintain a healthy weight.
Claim: Our metabolic rates can't change.
The truth: While it's true that genetics help determine our metabolic rates, we can boost metabolism by increasing lean muscle mass. Muscle burns more calories per hour than fat, which means that people with lean, muscular bodies need more calories to function than people with a higher percentage of body fat.
Our muscle mass decreases as we age, which slows metabolic rates by 2 to 8 percent per decade. But you can counteract this process by picking up the weights. "Having good muscle mass, especially towards your 40s and 50s, is important," says Manuel Villacorta, MS, RD, CSSD, registered dietitian. "If you start with a good baseline, your metabolism isn't going to decrease as much."
Claim: A diet of green tea and chili peppers will boost metabolism.
The truth: No magic food will speed up metabolism. Some studies have shown that green tea and hot chilies temporarily boost metabolic rates, but the lift isn't enough to offset eating too many calories.
"Just because you're putting a lot of chili peppers in your food doesn't mean you can eat more of it," says Villacorta. The path to healthy weight loss is through portion control and a balanced diet filled with nutrient-rich foods, not through a diet doused in chili peppers.
Claim: Eating late at night slows metabolism.
The truth: It's the extra calories – not when you eat them – that cause weight gain. There is little evidence to support the fact that eating after 8 p.m. causes weight gain. However, you may be more likely to snack mindlessly in the evenings while watching television. Calories in these snacks add up, and that can cause weight gain.
Claim: Very low calorie diets and skipping meals can jumpstart weight loss.
The truth: Weight loss is all about creating an energy deficit – ingesting fewer calories than your body expends each day – but creating too large of a calorie deficit can backfire. Our bodies are smart, and programmed for survival. Severely limiting calories can make your body think it's entering a famine, and that it needs to do more with fewer calories. Your body adapts to the restricted caloric intake, and uses fewer calories to perform the same tasks.
"We encounter people who are burning lots of calories, but not eating much, and they can't lose those last 10 pounds. Their metabolism is essentially on lock down," says Villacorta.