Everything you do with your body requires energy; from pulling a heavy snatch, to taking a nap afterwards, even the consumption and metabolism of food depends upon energy availability and it all adds up to influence your total daily energy expenditure (TDEE). This spontaneous generation of heat during catalytic reactions is called thermogenesis. When you calculate your TDEE, you’re really asking yourself a series of questions: “How much heat do I generate just to keep my organs functioning?” This is what defines your basal metabolic rate (BMR). Another factor in your daily energy expenditure comes from activity: “How much heat do I generate to fuel my exercise?”
The third, often overlooked contributor to TDEE and thermogenesis is nutrition. Ask yourself, “How much heat do I generate when I eat?” About 10% of your energy expenditure each day can be attributed to the Thermic Effect of Food (TEF). TEF describes the net loss of energy during the digestion and assimilation of nutrients. Because TEF contributes so little to daily energy expenditure, it doesn’t make sense for most people to worry about it but when you’re talking about getting very, very lean, every little bit counts.
The Thermic Effect of Different Macronutrients
When someone has a “fast metabolism”, they really have an inefficient metabolism that wastes more energy than it holds onto. Essentially, their metabolism works very hard, but they don’t get a lot done for all the fuss. The “cost” of operation is greater, so there’s less “profit”; less energy is stored. This can be good and bad, but the great thing is that you can manipulate your efficiency. A major factor in successfully taking advantage of the human body’s metabolic flexibility is consuming the right food, at the right time. Depending upon the composition, size and frequency of your meals, your body responds to your nutrition in markedly different ways.
Of all the macronutrients, alcohol produces the greatest thermic effect; that isn’t a good reason to chug a bottle of Jack, however, due to the fact that alcohol consumption puts the brakes on fat oxidation for a little while (Anne Raben). You’re actually more prone to store fat while you’ve got alcohol in your system, especially if you eat high-fat foods and drink at the same time (I’m looking at you, chicken wings!) Many people do report waking up “tighter” the morning after a night out drinking, but this has more to do with water loss than anything. Proper hydration is of the utmost importance to performing well and building muscle, so I would suggest taking it easy, but as they say: “To each his/her own.”
As far as everyday nutrition goes, protein is the most thermogenic of the three macros (carbs, protein and fat). This explains, in part, why people see improved body composition on high protein weight loss diets; you waste a lot of energy just breaking protein down. In addition, since you’ll feel more satisfied after eating a high protein meal, your drive to eat will be diminished (Halton). We recommend that protein consumption act as a base for the rest of your nutrition, and this is just one of many reasons. Not only are you providing your body with the material it needs to function and repair itself, but you’re keeping yourself lean.
Carbohydrate & Fat
Under normal circumstances, carbohydrate and fat are easier to break down and absorb. The TEF associated with these two macros is less than that of protein. Fat is the least thermogenic of the three. It may be interesting to note that when comparing obese and lean populations, the thermic effect of food is smaller regardless of the macros, but carbohydrate displays a greater thermic effect than fat; fat is even less thermogenic in obese individuals (R Swaminathan). Thus, consuming carbohydrates can contribute to increased net energy expenditure (K R Segal). We write about this all the time, but this sort of explains the concept: avoiding carbohydrates when you’re trying to lose weight really does slow down your metabolism. Conversely, if you’re trying to maintain muscle mass and conserve energy, eating low carb/high fat is a viable strategy.
Training and Post-Workout Carbs
Since you’re probably working out or weightlifting a few times a week, you’ll be glad to know that the thermic effect of food is more pronounced in active people than it is in sedentary individuals. This may be due to increased responsiveness to adrenaline signaling brought on by regular bouts of exercise (Nicole R. Stob). As I stated earlier, training creates a thermic effect too (exercise-associated thermogenesis). It’s more difficult to store energy after a workout, and that can be a good thing if you’re trying to maintain a lean body composition. It can also make it more difficult to build muscle mass, and that’s where carbs come in.
Carbs are normally pretty easy to break down and either utilize as an energy substrate, or to store as glycogen/fat but this changes for the better after training. The thermic effect of carbohydrate consumption after a single bout of exercise can be over 70% greater than before training (Charlene M. Denzer). That’s a difference of hundreds of calories every day, and thousands of calories every month, of food that you essentially get for free. Eating carbs post-workout kicks your metabolism into high gear, you burn up like a space shuttle during re-entry, and your body does whatever it can to cool down.
What this ultimately means, in practice, is that you can get away with eating large amounts of carbs to generate a significant insulin response and jam as much water, protein and other nutrients into your muscles as you can…Without worrying about getting fat. You get all of the hormonal and metabolic advantages of eating carbs without the bad. This is a great strategy to optimize recovery, performance and body composition all at once. This goes for both men and women, as well as lean and not-so-lean individuals. Verily, as far as body composition goes, post-workout is the best time to consume carbs.
Special Considerations: Intermittent Fasting, Yohimbine and Caffeine
The size of a meal seems to play a role in thermogenesis. While smaller meals eaten at a greater frequency create a more sustained thermic effect, larger meals produce an overall greater effect. Though the difference is small (somewhere around 50 calories a day), it does support the idea that eating more, less frequently, can make a positive impact on weight loss (M M Tai). If you follow an intermittent fasting protocol like LeanGains, you’re probably already taking advantage of this concept; if you aren’t, it’s yet another reason to delay breakfast and eat more at the end of the day.
In addition, certain substances can increase thermogenesis and help you mobilize fat. A common dietary supplement to consider, which you may already partake of, is good ol’ caffeine. One or two (or three, or four) cups of coffee can really get your metabolism humming and help you burn fat (K J Acheson). For leaner folks, Yohimbine (an herbal supplement) can augment the production of the catecholamines epinephrine and dopamine (Ostojica). More catecholamines can translate to increased thermogenesis, fat oxidation, and (potentially) an increased sense of well-being. Take caution though; it is not useful for everybody. You should be pretty lean before you consider supplementation. When adding anything atypical to your nutrition, be careful and start off very slow. If you have a history of cardiovascular disease, metabolic dysfunction, or there’s any question in your mind whether or not you’ll react well to a specific modification, you owe it to yourself to talk to a doctor.
In conclusion, you don’t really need to worry about any of this thermogenesis stuff. By simply eating protein and fat throughout the day, training hard, and having a nice carb-dense meal before and after your workouts, you’re already taking advantage of these concepts. I hope that by attaining deeper insight into the concepts we teach on Eat To Perform, you’ll understand how to dial things in a bit better and do what you need to get out of your own way. Knowledge is power, but I don’t want you to get side-tracked. I want you to focus on what really matters: eating well, training your ass off, and enjoying your accomplishments. Until next time!
- TDEE is influenced by basal metabolic rate and activity, but also metabolism of food
- “TEF” or the Thermic Effect of Food describes the net loss of energy during the digestion and assimilation of nutrients. It normally contributes makes up about 10% of your TDEE.
- Protein has the greatest TEF and fat has the lowest TEF. Carbs are in the middle.
- By eating carbohydrates after training, the TEF goes up drastically and more of the energy is lost as heat
- Eating larger meals less frequently contributes to a slightly greater thermic effect
- Caffeine and Yohimbine can help lean people increase thermogenesis and burn more fat
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