We all have that friend who seems to be able to eat whatever food they want but still maintains a six-pack year-round. They don't count calories; no foods are off-limits. Oh, how we secretly dislike this person!

The rest of us are forced to spend hours in the gym each week just to keep our waistline in check. The moment we let our portion control slip—even for a few days—it seems as if the weight piles on in all the wrong places.

Let me start by giving you good news: You can boost your metabolism! Probably not to the extent of your frenemy, but enough to help you feel less anxious about going back for seconds or having a piece of cheesecake.

What Is Metabolism?

Your metabolism—more precisely known as your resting metabolic rate—refers to the number of calories you burn in a resting state (think sitting, lying, sleeping). These calories are expended to carry out functions essential to survival, such as breathing, blood circulation, and oxygen and nutrient delivery throughout the body.

Your metabolism accounts for up to 70 percent of the calories you burn per day. The higher your metabolism, the more calories you burn. This means you may be able to eat more calories than a person of similar stature and better maintain your weight. And when you're dieting, this means you may be able to eat more calories to drive weight loss, which leads to a happier, less-hungry you. No wonder a "fast" metabolism is so desirable!  

Factors You Can—and Can't—Control

Your resting metabolic rate is influenced by several factors that are non-modifiable. These include your age, stature, sex, and genetics. As you age, your metabolism declines largely due to a decrease in fat-free mass. That means that as you get older, your body requires fewer calories to maintain your weight than it did the year before, all else being equal. As you can imagine, this compounds quickly. If you don't alter your exercise and eating habits, weight gain is likely.

Your body frame, independent of your muscle mass, is another factor that affects your metabolism beyond your control. The larger your body size, the faster your metabolism is likely to be, since your body needs to expend more energy to carry out essential functions across a larger area. And of course genetics influences everything, so even if you're the same age and size as someone else, your metabolic rates may still differ significantly.

Fortunately, your muscle mass also largely influences your metabolism. And you can directly influence the amount of muscle mass you have through your eating and exercise habits. Skeletal muscle is energetically costly tissue, which essentially means your body expends significant energy (calories) to maintain it. If you were to measure the metabolic rate of two people of the same size, but drastically different body compositions, you'd likely notice wildly different estimated values. By eating and training to optimize muscle growth, you'll set yourself up to enhance your metabolism.

Strategies to Boost Metabolism

1. Train With Weights Regularly

Resistance training induces muscle damage, which is necessary for muscle growth to occur. A study published in Medicine and Science in Sports and Exercise found that subjects who trained on a regular basis for six months experienced a 7 percent increase in their resting metabolic rate.[1] But you don't have to wait that long to see a boost in your metabolism: A strenuous bout of resistance training has been shown to elevate metabolic rate by as much as 11-12 percent for two hours post-workout, and even 9 percent for up to 15 hours post-workout.[2]

To fully capitalize on the benefits of resistance training, be sure your workout focuses on all the major skeletal-muscle groups with multijoint movements and multiple sets, and frequently targets the 8-12-repetition range, and even the 12-20 range on occasion.

2. Choose High-Intensity Exercise

The style of exercise you choose also has a major impact on your metabolic rate. After completing a bout of high-intensity exercise—think intervals or circuit-style resistance training—your oxygen consumption (sometimes referred to as excess post-exercise oxygen consumption, or EPOC), is elevated in an attempt to replenish substrates used up during exercise.[3,4]. This rise in EPOC elevates energy expenditure, potentially for up to 24-48 hours, which further impacts your metabolic rate long after your session ends.

3. Eat Enough Protein

Consuming dietary protein directly triggers muscle growth and repair. To maximize protein's muscle-building response, it's important that you're not only eating enough, but that you're eating it frequently throughout your day. Remember, the amount of muscle mass you have impacts your metabolic rate; to boost your metabolism, it makes sense to prioritize protein appropriately throughout the day.

In addition to eating sufficient protein at each meal, it's advantageous to spread your protein out in equal amounts across multiple meals rather than consuming it in just 1-2 large meals and a few protein-poor meals.[5] To maximally stimulate the muscle growth and repair response from protein, you must meet a minimum threshold every few hours, which for most of us is 25-35 grams of high-quality protein.

4. Stop Dieting Year Round

Long-term dieting can adversely impact your metabolism, because it causes your body to begin conserving energy, which then depresses your metabolism. It's been shown that long-term dieting negatively effects your total daily energy expenditure by reducing the number of calories you burn per day.[6] For every week you diet, aim to spend at least as many weeks off your diet. This will help provide adequate time for your metabolism to be restored to pre-diet levels and allow ample time to increase muscle mass. Ideally, the longer you can spend away from a calorie deficit, the better the impact you'll have on muscle mass, and ultimately your metabolism.

References

1. Lemmer, J. T., Ivey, F. M., Ryan, A. S., Martel, G. F., Hurlbut, D. E., Metter, J. E., ... & Hurley, B. F. (2001). Effect of strength training on resting metabolic rate and physical activity: age and gender comparisons. Medicine and Science in Sports and Exercise, 33(4), 532-541.
2. Melby, C., Scholl, C., Edwards, G., & Bullough, R. (1993). Effect of acute resistance exercise on postexercise energy expenditure and resting metabolic rate. Journal of Applied Physiology, 75(4), 1847-1853.
3. Paoli, A., Moro, T., Marcolin, G., Neri, M., Bianco, A., Palma, A., & Grimaldi, K. (2012). High-Intensity Interval Resistance Training (HIRT) influences resting energy expenditure and respiratory ratio in non-dieting individuals. Journal of Translational Medicine, 10(1), 237.
4. Skelly, L. E., Andrews, P. C., Gillen, J. B., Martin, B. J., Percival, M. E., & Gibala, M. J. (2014). High-intensity interval exercise induces 24-h energy expenditure similar to traditional endurance exercise despite reduced time commitment. Applied Physiology, Nutrition, and Metabolism, 39(7), 845-848.
5. Mamerow, M. M., Mettler, J. A., English, K. L., Casperson, S. L., Arentson-Lantz, E., Sheffield-Moore, M., ... & Paddon-Jones, D. (2014). Dietary protein distribution positively influences 24-h muscle protein synthesis in healthy adults. The Journal of Nutrition, 144(6), 876-880.
6. Leibel, R. L., Rosenbaum, M., & Hirsch, J. (1995). Changes in energy expenditure resulting from altered body weight. New England Journal of Medicine, 332(10), 621-628.