Do you know people who complain about having a slow metabolism and how they barely eat anything yet still gain weight? Or have you met people who complain about someone they know who can eat whatever he or she wants (including large portions of junk food!) due to a fast metabolism and apparently never gain weight? In both cases the individual usually ends by saying, “It’s not fair!” These scenarios raise a question: is metabolism really the culprit? And if so, is it possible to fire up your metabolism to burn more calories?
Metabolism or metabolic rate is defined as the process by which your body converts what you eat and drink into energy. During this process, calories in food and beverages are combined with oxygen to release the energy your body needs to function. Even when you’re at rest, your body needs energy for all its “hidden” functions, such as breathing, circulating blood, adjusting hormone levels, and growing and repairing cells. The number of calories your body uses to carry out these basic functions is known as your basal metabolic rate (BMR). Your BMR is partly determined by the genes you inherit.
Other factors determine your individual BMR including:
• Body size and composition. People who are larger or have more muscle burn more calories, even at rest.
• Sex. Men usually have less body fat and more muscle than do women of the same age and weight, which means men burn more calories.
• Age. As you get older, the amount of muscle tends to decrease and fat accounts for more of your weight, slowing down calorie burning.
• Food processing (thermogenesis). Digesting, absorbing, transporting and storing the food you consume also takes calories. About 10 percent of the calories from the carbohydrates and protein you eat are used during the digestion and absorption of the food and nutrients.
• Physical activity. Physical activity and exercise, such as playing tennis, walking to the store, chasing after the dog and any other movement, account for the rest of the calories your body burns up each day. Physical activity is by far the most variable of the factors that determine how many calories you burn each day.
One way to think about metabolism is to view your body as a car engine that is always running. When you’re sitting still or sleeping, your engine is idling like a car at a stop light. A certain amount of energy is being burned just to keep the engine running. Of course, for humans, the fuel source is not gasoline. It’s the calories found in foods we eat and beverages we drink – energy that may be used right away or stored (especially in the form of fat) for use later.
How fast your body’s “engine” runs on average determines how many calories you burn. If your metabolism is “high” (fast), you will burn more calories at rest and during activity. A high metabolism means you’ll need to take in more calories to maintain your weight. That’s one reason why some people can eat more than others without gaining weight. A person with a “low” (slow) metabolism will burn fewer calories at rest and during activity and therefore has to eat less to avoid becoming overweight.
It’s part truth and part myth that metabolism is the key to weight. The rising tide of obesity in this world can’t be blamed entirely on an inherited tendency to have a slow metabolism. Something environmental (changes in diet and exercising too little) are much more likely culprits.
Regardless of whether your metabolism is fast or slow, our bodies are designed to store excess energy in fat cells. So, if you eat and drink more calories than your body expends, you will gain weight. On the other hand, if you eat and drink fewer calories than are burned through everyday activities (including exercise, rest and sleep), you’ll lose weight. Our bodies are also programmed to sense a lack of food as starvation. In response, our BMR slows down, which means fewer calories burned over time. That’s one reason why losing weight is often difficult.
While you don’t have much control over the speed of your basal metabolism, you can control how many calories you burn through your level of physical activity. The more active you are, the more calories you burn. In fact, some people who are said to have a fast metabolism are probably just more active — and maybe fidget more — than others.
You can burn more calories with:
• Regular aerobic exercise. Aerobic exercise is the most efficient way to burn calories and includes activities such as walking, bicycling and swimming. As a general goal, include at least 30 minutes of physical activity in your daily routine. If you want to lose weight or meet specific fitness goals, you may need to increase the time you spend on physical activity even more.
• Strength training. Experts recommend strength training exercises, such as weightlifting, at least twice a week. Strength training is important because it helps counteract muscle loss associated with aging. And since muscle tissue burns more calories than fat tissue does, muscle mass is a key factor in weight loss.
• Lifestyle activities. Any extra movement helps burn calories. Look for ways to walk and move around a few minutes more each day than the day before. Taking the stairs more often and parking farther away at the store are simple ways to burn more calories. Even activities such as gardening, washing your car and housework burn calories and contribute to weight loss.
When it comes to weight, metabolism is important and does have a genetic component. Whether you can change your metabolic rate, however, is a matter of considerable debate. Clearly, you can change how you balance the calories you take in against the calories you burn up through activity, which can change your weight.
Don’t look to dietary supplements for help in burning calories or weight loss. Products that claim to speed up your metabolism are often more hype than help, and some may cause dangerous side effects. There’s no easy way to lose weight. The foundation for weight loss continues to be based on physical activity and diet. Take in fewer calories than you burn, and you lose weight.
References:
https://www.health.harvard.edu/diet-and-weight-loss/does-metabolism-matter-in-weight-losshttps://www.mayoclinic.org/healthy-lifestyle/weight-loss/in-depth/metabolism/art-20046508 
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