When it comes to weight loss supplements and fat burners, the words “thermogenesis” and “thermogenic” are used frequently. Based on the way these two words are splashed across advertisements, you’re led to believe it’s a good thing to boost, increase, or enhance. But have you ever wondered what a thermogenic or thermogenesis means, or why you would want to increase it? Hang in there, keep reading and we'll explain all the ins and outs of thermogenesis and why you want your fat burner to increase it, especially if you want to drop the fat fast.
What is Thermogenesis?Thermogenesis is the metabolic process by which organisms burn calories in order to generate heat. A simpler way to say that is thermogenesis is the body’s way of producing heat. It does this by “burning” calories. Thermogenics are ingredients or supplements that help increase the production of heat in the body, and as a result, increase the number of calories you expend. This translates to greater calorie burn throughout the day, which in theory, should help you lose weight faster. There are a number of ingredients commonly touted as thermogenics, which we’ll get to a little later in this article, but first, let’s take a moment to review the different types of thermogenesis that occur in the body.
Types of Thermogenesis
On the surface, thermogenesis seems fairly straightforward -- it’s how your body produces heat. But, as it turns out, there’s not just one type of thermogenesis. Science has broken it down into three (or four, depending on the classification scheme) types. So, with that in mind, let’s take a second to review each of the different forms and discuss what separates them from one another.
Basal Metabolic Rate (BMR)Basal metabolic rate (BMR) consists of the calories your body burns to carry out essential functions for survival. This includes such things as circulating blood throughout the body, breathing, etc. Essentially, BMR accounts for the energy to perform vital body processes while you’re at rest. It’s the number of calories your body burns if you did nothing but lay in bed all day long. Basal metabolic rate is the largest contributor to energy expenditure during the day, <1> accounting for 60-75% of total calories burned.
Diet-Induced ThermogenesisThe second type of thermogenesis is diet-induced thermogenesis. Scientists have defined diet-induced thermogenesis as: “the increase in energy expenditure above basal fasting level divided by the energy content of the food ingested and is commonly expressed as a percentage”. A simpler explanation of diet-induced thermogenesis would be, the number of calories you burn eating, digesting, absorbing, and transporting nutrients from the food you ate. Now, here’s where things get interesting, each macronutrient has a different thermic effect of food, meaning that your body burns different amounts of calories depending on what type of food you’re eating. So, let’s take a look at that now:
- Protein - The most metabolically demanding macronutrient for your body to digest and absorb. Its thermic effect of food is about 20-35%, which means that if you eat a piece of protein that contains 100 calories, depending on what type of protein it is, your body will burn 20-35 calories simply trying to break down that food.
- Carbohydrate - After protein, carbohydrate is the next most metabolically demanding macronutrient to digest and absorb. Its thermic effect of food is 5-10% of calories consumed.
- Fat - The least calorie-intensive macronutrient to digest and absorb is fat. It has a thermic effect of food of about 5%.
- Protein = 25 grams * 4 calories/gram = 100 calories
- Carbohydrate = 3 grams * 4 calories/gram = 12 calories
- Fat = 2 grams * 9 calories/gram = 18 calories
- Protein = 25% * 100 calories = 25 calories burned
- Carbohydrate = 10% * 12 calories = 1.2 calories burned
- Fat = 5% * 18 calories = 0.9 calories burned
Energy Cost of Physical ActivityThe final form of thermogenesis comes from your daily activity. Exercise scientists have further divided this category into two “subcategories”, which is why we said there were four types of thermogenesis at the top. Those two subcategories are:
- Exercise Activity Thermogenesis
- Non-Exercise Activity Thermogenesis (NEAT)
Exercise Activity Thermogenesis, as you probably guessed, is the calories your body expends during any type of exercise you perform. This includes weight lifting, steady-state cardio (walking or jogging), high-intensity interval training, CrossFit, etc. Basically, any type of structured physical activity that’s more intense than just walking from point A to point B falls under this subcategory. Non-Exercise Activity Thermogenesis describes the number of calories you expend in all other physical activity that isn’t specifically “exercise”. This number is highly variable depending on how much you move around during the day. Combining both exercise activity thermogenesis and non-exercise activity thermogenesis gives us our total energy cost of physical activity each day. This number can vary between 15-30% of your total daily energy expenditure, depending on how active you are on a given day. This constitutes all the major contributors to daily thermogenesis. Add each of these three major categories up, and you have your total daily energy expenditure. Now, let’s look at a few outside factors that could potentially increase thermogenesis.
Thermal StressThermal stress refers to the impact the temperature of the environment has on your body temperature. You see, while we can survive in any number of climates, your core temperature has a very limited range that is considered safe. Go any higher or lower than this range, and things start going very bad, very quickly for you. The body can only tolerate a drop-in body temperature of approximately 10 degrees Fahrenheit, and a rise in temperature of 5 degrees Fahrenheit. If the average temperature of a person is 98.6 degrees Fahrenheit, this gives you a “safe range” of about 88.6-103.6 degrees Fahrenheit. Note that this is the range your body can survive. It’s certainly not optimal to be at the extremes of this range though. So, what happens if you do start to drift too far away from the typical 98.6-degree core temperature? Fortunately for you, the hypothalamus has that handled. When it gets too hot and your core temperature starts to rise, your body will use one of four processes to cool you off:
Heat leaves the body via evaporation when you sweat and breathe. Additionally, your body will also move warm blood to superficial blood vessels (ones closer to the skin). Note that this can lead to a reddish or flushed appearance. When it’s too cold outside (blizzard in the middle of winter), your body tries to keep warm. It does this by pulling blood away from your hands, feet, face, and directing it towards your core, which keeps your better insulated. Your body can also increase thermogenesis by shivering, which keeps you warm and significantly boosts metabolism! In both of these scenarios, your daily thermogenesis (and total daily energy expenditure) is ramped up considerably. Now, a lot of people will take this thermal stress effect and attempt to train in very hot or very cold environments. While it may seem like a good idea to train in adverse climates, in the effort to create an even greater calorie burn, the truth is, it wouldn’t be all that effective. You see, when you train in extreme climate conditions, your performance suffers substantially, so while your body might be burning more calories trying to maintain its temperature, your actually not having as effective of a workout as you would be if you were training in a more “normal” training environment. We’ve just about covered everything that can impact thermogenesis on a day in, day out basis, except supplements. As we stated at the beginning thermogenic supplements make up a huge portion of the weight loss supplement market, but...
Can Supplements Actually Increase Thermogenesis?
YOU BET they do! Sports nutrition scientists have discovered several supplements that do increase thermogenesis, and research confirms as much. These thermogenic supplements increase energy expenditure, helping you burn more calories each day (even while you rest!) and lose fat faster.