Metabolism: it's a term thrown around a lot in the health and fitness world. Unfortunately, it's often used with promises of quick fixes and miracle solutions (how many times have you heard someone claim you need to "fix" your metabolism?).
But what exactly is metabolism? Simply put, it's the process by which your body converts what you eat and drink into energy. Our Basal Metabolic Rate is simply the energy we burn throughout the day to stay alive. It costs energy to pump our heart, the exchange oxygen & CO2, to build up / break down proteins and other structures.
Believe it or not, your BMR is the largest part of your energy expenditure throughout the day! It contributes between 60-70% on your total calorie burn. Factors that influence the amount of calories you burn at rest include:
Our Bodyweight: This one is pretty simple, the larger we are, the more weight we need to maintain. The more we have to maintain, the more energy it costs. Many make the mistake of assuming once they have gone through a fat loss phase and reached their ideal bodyweight they can just go back to eating the same amount of food as they did pre-diet. However, since you are now a smaller individual, the energy cost to maintain everything is less.
Muscle Mass vs Fat Mass (Body Composition): You may have heard before that muscle burns more calories than body fat. While the numbers are going to vary based on who you talk to, most research suggests that you burn around 6 calories per pound of muscle per day [1]. If we really want to be nitpick, we could argue that the number is slightly higher since our total energy expenditure also includes movement, not just lying down. So if our total mass goes up 1%, we're going to burn 1% more. For most of us though, it's good enough to just understand that the more muscle we have, the more calories we will burn throughout the day
Age (Kinda): It is very common to hear older clients say "I don't burn as many calories as I used to which is why I can't lose weight" or "My metabolism is broken". To be fair, changes happen as we age that can absolutely cause our BMR to go down. However, there is also an explanation for this that has gone through extensive research [1]. When you look at basal metabolic rate and correct for lean body mass (as shown below), BMR stays constant from age 20-60. As we hit ~40 years of age, we start to see something called sarcopenia which is a loss of muscle mass (can be significantly reduced with resistance training) which as seen below will absolutely affect how many calories we burn. Once we hit ~60 years of age, there seems to be a small reduction irregardless of Muscle Mass or Fat Mass. However, this seems very small (0.7% per year)
So, how can you boost your metabolism the right way, without falling for gimmicks and short-lived fixes?
Things That Appear To Work
Building Muscle (Resistance Training)
If your goal is to either increase your metabolic rate throughout the day or at least maintain it as best as possible throughout a fat loss phase, resistance training is almost an absolute must. On average, one pound of muscle burns approximately 6 calories per day [2] at rest, and then as we build muscle it appears that the calories we burn during activity increases in a linear fashion.
In comparison, body fat being less metabolically active only burns about 2 calories at rest. So as we improve our body composition (ratio of lean muscle mass and body fat) our metabolism should be higher.*
* Note the study above - decreases in metabolism over lifespan can be closely tied to losses in muscle mass (Sarcopenia)
Conservative Fat Loss Phases
This one is somewhat related to the muscle mass point. When we recommend weight loss targets, we suggest a calorie deficit that equates to roughly 0.5 - 1.0% of bodyweight per week. For example, a 200lb man looking to lose weight should aim for 1-2lbs per week.
The reason we suggest this is to protect the muscle mass we have. In fat loss research, you typically will see a 3:1 ratio of fat vs muscle loss (eg. if someone loses 10lbs, you can expect roughly 7.5lbs coming from body fat and 2.5lbs coming from muscle). This ratio can be greatly improved by ensuring adequate protein intake as well as lifting weights.
The greater the deficit, the more muscle mass you are likely to lose, which ends up hurting us in future weight loss attempts. This is why multiple yo-yo diets makes things difficult.*
* If you are someone who has a history of aggressive diets, followed by a rebound, don't worry. Your metabolism is NOT broken, but you may want to consider adopting a less aggressive, more periodized approach with some time where the focus isn't on "losing weight".
Adopting an Active Lifestyle
Rather than focusing on short-term fixes, aim to build health and fitness into your lifestyle in a way that you can maintain for years to come. Increasing your activity throughout the day won't necessarily impact your Basal Metabolic Rate, but it will increase your Active Metabolism which absolutely moves the needle.
Find activities that you enjoy and make them a regular part of your routine. Whether it's hiking, swimming, dancing, or lifting weights, find what works for you and stick with it. It could even be things as small as parking further from the mall entrance or taking the stairs instead of the elevator.
Additionally, prioritize nutrient-dense foods that support a healthy metabolism, such as lean proteins, whole grains, fruits, and vegetables.
Things That Work......Kinda
Cardiovascular Training
When talking cardio, we want to make it clear that while it doesn't necessarily affect our resting metabolism, conditioning does indeed burns calories so it's going to make the list.
One thing to consider with cardiovascular training is that although you will burn calories, there appears to be a compensatory effect that we need to be aware of. [3] Simply put, if we burn energy through cardio, our bodies have a sneaky way of self-regulating by decreasing the amount that we move throughout the day. Burning 500 calories on the Stairmaster may result in us reducing movement throughout the day, decreasing our energy consumption by 100 calories.
It appears that some people tend to compensate more than others, which would limit their ability to lose body fat. Some may even compensate more (eg. burned 500 calories, reduce non-exercise activity by 400 calories) creating an uphill climb. This is why we track steps with our nutrition clients. We want to get ahead of any compensations to drive the adaptation we want.
Even though the effect isn't as large as you may have thought, there is still an effect here. That's why we're putting it in the "kinda" section. There are also a slew of other reasons why we do cardio. We do it for health, the heart, the lungs, the things that are going to improve your odds of living a long life. Do cardio, just make sure you do it in conjunction with the things above.
This is important: We want you to do conditioning, but we also want you to understand that we cannot out-train a poor diet. Cardio alone will not get you out of the hole you're in if you don't address eating and lifestyle patterns. If you need help, book a free consult with one of our certified nutrition coaches.
Things That Don't Work
There are a lot of claims out there in the fitness industry that to be fair hold some truth. The problem is that they're usually blown out of proportion, and unfortunately it's at the cost of your hard earned money. Then there are things that just flat out don't work. We'll go through both here:
Detoxes / Cleanses
Detoxes often claim to aid in fat loss by eliminating toxins from the body, but the reality is that they typically don't work for sustainable fat loss. There a very few (if any) research papers that support the idea that a diet will "remove toxins" from your body. If you have a liver, you're covered.
Detoxes may often lead to initial weight loss, but this is mostly due to water weight loss, not fat loss. Once you resume your normal eating habits, the lost water weight typically returns. In reality, many detox diets are low in essential nutrients like protein, healthy fats, and certain vitamins and minerals. This can lead to nutrient deficiencies and negatively impact overall health.
Finally, they often involve extreme dietary changes that are difficult to maintain over the long term. Once you stop the detox, you're likely to return to your previous eating habits and regain any lost weight.
Meal Frequency
This one may actually surprise people, and it's something that I've changed my mind on over the last couple of years. We used to think that spreading out our meals in greater frequencies throughout the day lead to that metaphorical "constant burning of our metabolic fireplace". However, when you look at the studies on this, it doesn't seem to pan out. [4] [5]
It is important to note that if spreading out your calories into more meals is a way to stay full throughout the day, go for it. It's also a great way to spread out feedings of protein in a day. Adherence is often the most important factor in a fat loss diet. However, from a metabolism perspective, there doesn't seem to be much there.
Fat Burners and Some Other Supplements
Thermogenic supplements are supplements that contain a bunch of random ingredients, many of them being stimulants, and the idea is that they will burn calories at rest. Like many supplements on the market, they have a tendency to market to an individual's pain points and leaves you disappointed in the end.
Most original fat burner formulas were ephedra-based, which although had some potential effectiveness also caused some safety concerns. Nowadays, most fat burners are a combination of Caffeine, L-Carnitine, Amino Acids, and more. Many of these when you look at the label fall far below the minimum effective doses to really have an effect.
So the question is, what's the proposed mechanism? How do supplement companies claim they work? Since they are full of stimulants, Fat Burners will increase thermogenesis by activating a sympathetic response (otherwise know as a "fight or flight" response). The idea is that you will burn more calories at rest this way. The problem is that the actual effect is in reality very small, it's gone quickly, and you'll probably be pretty low-energy when you stop taking them.
Conclusion
In conclusion, while there may be tempting shortcuts and quick fixes touted as metabolism boosters, the most effective way to improve your metabolic rate is through sustainable lifestyle changes. By incorporating regular physical activity, strength training, and healthy eating habits into your routine, you can boost your metabolism and achieve long-term success in your health and fitness goals. Remember, it's not about quick fixes—it's about building a lifestyle that supports your overall well-being.
[1] Pontzer, H., Yamada, Y., Sagayama, H., Ainslie, P. N., Andersen, L. F., Anderson, L. J., Arab, L., Baddou, I., Bedu-Addo, K., Blaak, E. E., Blanc, S., Bonomi, A. G., Bouten, C. V. C., Bovet, P., Buchowski, M. S., Butte, N. F., Camps, S. G., Close, G. L., Cooper, J. A., Cooper, R., … IAEA DLW Database Consortium (2021). Daily energy expenditure through the human life course. Science (New York, N.Y.), 373(6556), 808–812. https://doi.org/10.1126/science.abe5017
[2] Wang, Z., Ying, Z., Bosy-Westphal, A., Zhang, J., Schautz, B., Later, W., Heymsfield, S. B., & Müller, M. J. (2010). Specific metabolic rates of major organs and tissues across adulthood: evaluation by mechanistic model of resting energy expenditure. The American journal of clinical nutrition, 92(6), 1369–1377. https://doi.org/10.3945/ajcn.2010.29885
[3] Careau, V., Halsey, L. G., Pontzer, H., Ainslie, P. N., Andersen, L. F., Anderson, L. J., Arab, L., Baddou, I., Bedu-Addo, K., Blaak, E. E., Blanc, S., Bonomi, A. G., Bouten, C. V. C., Buchowski, M. S., Butte, N. F., Camps, S. G. J. A., Close, G. L., Cooper, J. A., Das, S. K., Cooper, R., … IAEA DLW database group (2021). Energy compensation and adiposity in humans. Current biology : CB, 31(20), 4659–4666.e2. https://doi.org/10.1016/j.cub.2021.08.016
[4] Schoenfeld, B. J., Aragon, A. A., & Krieger, J. W. (2015). Effects of meal frequency on weight loss and body composition: a meta-analysis. Nutrition reviews, 73(2), 69–82. https://doi.org/10.1093/nutrit/nuu017
[5] Munsters, M. J., & Saris, W. H. (2012). Effects of meal frequency on metabolic profiles and substrate partitioning in lean healthy males. PloS one, 7(6), e38632. https://doi.org/10.1371/journal.pone.0038632