The TDEE formulas are derived from an average of people following a typical westernized/modern diet. This kind of diet is high carbohydrate and made up of at least 70 to 80 percent of plant foods (keep in mind that almost all junk food, soft drinks, etcetera are made from plant foods and plant (seed) oils). And we know that plant foods contain fiber (that binds up proteins and makes them non-absorbable), antinutrients (that block minerals), contains no usable vitamins and a lot of toxins that causes inflammation, and that the carbohydrate content (starches) is mostly indigestible – especially if the ‘food’ have been re-heated. This means that on a typical ‘fitness’ diet, your calorie- and macronutrient program might show 200g protein, 200g carbohydrates, 80g fat, and 2300 kcal. But in reality, you might only absorb 160g protein, 120g carbohydrates, 60g fat, and get only 1700 kcal! And if you have gut issues, as most people who consume plant foods have, you may absorb even less. In other words, these ‘energy requirement’ calculations are very skewed.

With that in mind, what do you think will happen when you go full animal-based/carnivore and you actually absorb 91 to 95 percent of what you consume? Yes, you will only need 60 to 70 percent of the ‘calories’ you used to consume if you use the same TDEE formula. And no, this will not make you hungry as a nutrient-dense animal-based diet will cover all your nutritional needs. Hunger and cravings are simply a sign of nutrition deficiencies.

It’s also important to understand that there are no calorie receptors in our body. Your body does not measure how many calories it gets. It has no idea. Calories are a concept of physics, not a concept of physiology. Calories is simply a unit of heat-energy from burning something and increasing the temperature of a given mass of water by 1 °C. That is not how our bodies work. Also, if you place 100 calories of sugar in your mouth, the physiological response is totally different from if you were to place 100 calories from animal fat in your mouth.
If you swallow that sugar, you get an insulin response. If you swallow the fat, you get no insulin response at all. The body responds to hormones and that is how it knows what to do when you have consumed something.
If you consume carbohydrates, insulin will go up. If you consume protein, insulin will go up, and so will your protein synthesis by the activation of mTOR and some other signaling pathways.
In other words, there are different receptors for amino acids, for fat, and for hormones that will be activated by what we eat or do.

If your nutritional base is covered, your inclination to overeat will be very low and since you consume nutritional-dense animal foods, you will be satiated very quickly. Your body will also be much more efficient and your food absorption will be top-notch, which means that your need for ‘calories’ will be much lower than someone with gut issues and bad absorption (as in vegans, vegetarians and most people following a typical modern diet with harmful foods).
In other words, energy requirements, as in ‘calories’, varies greatly from person to person. It’s not as simple as muscle tissue, metabolic rate and activity levels, it’s also about food choice and composition, general health, hormone levels, and especially gut health.

So, as a coach, when someone is switching to an animal-based diet, I look at previous nutritional habits and diets, medication, gut health, muscle mass and body weight, daily activity, exercise, and a lot more. I use several calculations as well as experience to get to a ‘calorie’ baseline where we will start. From there it’s all about observation and feedback. Every 2 to 3 weeks we evaluate and adjust the intake of food. And when adjusting, it’s not only about the energy within the food, it’s about macronutrient ratios, choice of food stuff/sources (replacing/switching things around to get where we want to go), and so on.
Also, as your body heal, your gut flora improves, and previous hormone imbalances get resolved, your energy needs will shift and then stabilize. And in the end, when you’re healthy in body and mind, you will instinctively eat what you need and when you need to. When following our natural diet, it’s actually very simple. And in the end, all you need to do, from time to time, is to evaluate your progress toward your goals and adjust from there.