By Lizzie Streit, MS, RDN, LD 

In most people’s minds, a fast metabolism translates to thinness and easy weight loss. That’s why there are countless dieting products that claim to boost metabolism, and just as many media headlines pertaining to the topic. 

Some claims suggest that you can burn more calories by eating spicy foods, small meals, or taking pills and powders, while others blame genetics for a sluggish metabolism. Plus, there’s the mystery of how someone can eat like a horse without gaining weight, while another person may see their weight jump after a single night of indulgence. 

With all of this conflicting noise, how can you really know what to believe? Thankfully, this post breaks down common myths about metabolism and presents the facts. 

But first, you need to understand what exactly metabolism is and what affects it. 

What is metabolism? 

In short, metabolism is the process by which the body burns energy from food to support its functions and keep your heart beating, lungs breathing, and every cell working.  

This definition of metabolism is technically known as the basal metabolic rate (BMR), or the number of calories the body needs to function at rest. The body also burns calories through physical activity and food breakdown, known as the thermic effect of food, but metabolism as we hear about it is almost always referring to BMR. 

A fast metabolism burns more calories to support bodily functions than a slow metabolism, which means that fewer calories get stored as fat. Since burning more calories than you consume is key to losing weight, it makes sense that people associate a fast metabolism with easier weight loss. 

Several factors affect the speed of your metabolism, including age, gender, weight, hormones, and genetics. While some of these factors are out of your control, there are still ways to maintain a healthy metabolism through diet and lifestyle habits. Check out our post on tips to boost metabolism, and keep reading to learn about common metabolism myths. 

Metabolism Myths 

Myth: You need to eat the same number of calories every day for a healthy metabolism. 

Truth: Maintaining a calorie deficit is a part of weight loss, but you don’t need to eat a precise number of calories every day. Furthermore, not every calorie is created equal. More energy is necessary to process some types of calories (like those from protein), and even the time of day can change how calories from food are used. Plus, cutting calories too much can actually slow down metabolism by signaling to your body that it needs to enter survival mode, especially if you eat fewer than 1,000 calories per day (1, 2). 

Decreasing calorie intake is still an important part of losing weight, but it’s not an exact science. What’s important is that the average amount of calories you eat over the course of week is generally less than you burn, and that you mainly focus on eating a balance of healthy foods and macronutrients.  

Myth: Metabolism is genetic and you can’t do anything about it. 

Truth: While genetics do influence metabolic rates, they don’t make your metabolism totally unchangeable. In other words, if you are genetically predisposed to a slower metabolism, there are still ways that you can boost it. Building lean muscle mass has been shown to increase metabolic rates, mainly because muscle uses more energy at rest compared to fat (3). 

On a similar note, aging may slow metabolic rate due to the decrease in muscle mass that occurs as you age. But keep in mind that you can counteract this decline by staying active and doing muscle-building exercises. 

Myth: Thin people have faster metabolisms. 

Truth: Fast metabolism is often associated with weight loss, but thin people don’t necessarily have a quicker metabolic rate. People at heavier weights actually require more energy at rest than thinner people, just by nature of having more body mass. 

And remember what we just said about lean muscle being more metabolically active? At the same weight, a thin person with more muscle mass will burn more calories than someone with less lean mass. As you can see, both total body weight and body composition matter. The key is to eat enough calories to keep your metabolism from slowing down, but not too much that you exceed your energy needs. Lifting weights and building muscle also helps. 

Myth: Eating small but frequent meals is better than eating fewer, larger meals. 

Truth: It’s a common belief that eating smaller meals and decreasing time between meals is best for your metabolism. However, there is no substantial evidence to support this myth (4). 

Eating small meals in frequent intervals may prevent you from getting hungry in between meals and overeating as a result. In turn, this can help with weight loss for some people. But in terms of the metabolism boosting benefits of this habit? There aren’t any. 

Myth: Spicy foods, green tea, and coffee help boost metabolism. 

Truth: The energy boost or kick in the pants that you may feel from hot peppers, green tea, or coffee is commonly associated with a boost in metabolism. And technically, it is true that compounds in these foods may speed up metabolic rate…but only a little and for short periods of time (5, 6, 7). 

Since coffee has been linked to small increases in metabolism, you may also wonder if caffeinated energy drinks would have the same effect. Sure, caffeine may have marginal benefits for metabolism, but the high amounts of sugar in most energy drinks outweighs any possible benefits. 

If you enjoy green tea, coffee, or hot peppers, there’s no harm in adding them to your diet in moderation. But remember, they’re not a magic bullet for a fast metabolism. 

The Bottom Line 

What exactly dictates a person’s metabolism isn’t entirely understood, but it appears that genetics, age, and modifiable factors like body composition play a role. 

So instead of falling for one of the latest metabolism myths, aim to eat a nutritionally balanced diet with enough calories and protein, stay active, and work on building and maintaining muscle mass. For more tips, be sure to check out these other simple ways to boost metabolism. 

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