Quickly and easy calculate your optimal daily intake with our protein intake calculator.
You know protein is important. You know that your protein requirements depend on your health goals, and that protein can minimize fat gains during the holidays and help with dieting in general.
But here are five interesting facts you still might not know.
1. Thermic effect of food
The thermic effect of food (TEF), also known as dietary induced thermogenesis (DIT) and specific dynamic action (SDA), represents the energy (the calories) you need to spend to process what you eat. The TEF consists of two separate components: obligatory and regulatory. The obligatory component represents the energy required to digest, absorb, and metabolize the food. The regulatory component represents the energy lost as heat.[1]
In other words, your body needs to use energy to extract energy from the food you eat. The TEF represents about 10% of the caloric intake of healthy adults eating a standard mixed diet, but your actual number will depend on several factors, which include your lean body mass and the size and composition of your meal.
The bigger your meal and the more lean mass you carry, the longer you’ll keep spending energy to process the food, which is why the TEF should be measured for at least five hours after the meal was eaten.[2] And the composition of the meal matters because the different macronutrients have different TEFs:[3]
Fat: 0–3%
Carbohydrates: 5–10%
Protein: 20–30%
Although it represents but a small percentage of your daily caloric expenditure, the TEF can still amount to several hundred kilocalories each day and so could affect your body composition over the long term. Now you might think, judging from the numbers above, that increasing your protein intake should help you diet down. And well, yes, it should, but probably not because of the resulting increase in TEF — not directly, at least.
One analysis reported that, while protein was the only significant determinant of the total TEF, every 1% increase in calories from protein was associated with a mere 0.22% increase in the total TEF.[4] Based on these findings, if you were to double your protein intake from 15% to 30%, your daily TEF would increase by only 3.3%. So for each 2,000 kcal you consume (a number that might represent your total daily needs), you’d be spending an additional 66 kcal — a number easily offset by one small apple or a handful of potato chips.
Your body burns more energy digesting protein than it does either carbohydrate or fat, yet increasing your protein intake has a negligible effect on your energy expenditure.
However, while increasing your daily TEF by consuming more protein isn’t likely to have a direct effect on weight loss, as we saw, increasing the TEF of a meal might promote weight loss indirectly by increasing satiety, as we’ll see.
2. Satiety
Satiety and satiation are often used interchangeably to mean “satisfying hunger”. Technically speaking, however, satiation describes the lack of desire to continue eating a meal, whereas satiety is the feeling of fullness that allows us to stop eating for a while. In this article, when we use the adjective satiating, as in the paragraph below, we refer to satiety.
Protein is the most satiating macro,[5] especially for women,[6] which helps explain why high-protein diets promote weight loss and weight-loss maintenance.[7] But why is protein especially satiating?
Although many hormones play a role in regulating appetite,[8] three intestinal hormones have received special attention: cholecystokinin (CCK), glucagon-like peptide-1 (GLP-1), and peptide YY (PYY).[9][10] Yet none of the three seems a good predictor of the effect that eating more or less protein will have on total food intake, as evidenced by a meta‐analysis of nine studies involving a total of 117 healthy, normal-weight men.[11] Rather, other factors — such as protein’s high TEF — may explain the satiating effect of high-protein diets. In lean women, greater 24-hour TEF was shown to correlate with greater satiety.[12]
One meta-analysis of individual-participant data from five randomized meal-test studies reported no significant association between satiety and protein intake, but only 8 of the total 111 participants had received meals in which >20% of calories came from protein,[13] whereas protein seems to increase satiety only when it makes for 25–81% of a meal’s calories.[5] Therefore, the lack of an association between satiety and protein intake reported in the aforementioned meta-analysis may apply only to meals with a normal protein content (about 15% of calories).[13] In other words, the TEF of a meal increases satiety only when the meal is high in protein.
Eating protein may also promote satiety by increasing the rate of intestinal gluconeogenesis (IGNG) — the rate of glucose production within intestinal cells.[14][15] Currently, only rodent studies exist to suggest that IGNG is a key signal to the brain with regard to energy homeostasis, but important enzymes involved in gluconeogenesis have been found in the small intestine of humans, suggesting that IGNG may also take place within us.[16]
Finally, amino acids may promote satiety by directly affecting the brain.[17] Specifically, they appear to activate mTOR and suppress AMPK within hypothalamic and arcuate nucleus neurons, thus causing a decrease in the orexigenic neuropeptide Y and an increase in the anorexigenic peptide α-MSH.[18] The branched-chain amino acid (BCAA) leucine appears to be particularly satiating;[19][20] and can reduce food intake when directly injected into the brains of rodents.[21]
Protein increases satiety more than carbohydrate and fat do, by increasing thermogenesis and through the direct effect of its constituent amino acids (notably leucine) on the brain.
Everything you need to know about whey protein
Whey protein is far more complex than you'd think - supplement companies are always trying to pull a fast one over you with legal loopholes and proprietary blends.
Our Definitive Guide to Whey Protein breaks down everything you need to know about whey protein so you can buy the best whey protein for you.
3. You don’t need protein, you need amino acids


Your body does not need protein; instead, of the 20 amino acids that make up dietary protein, your body needs to consume the 9 it cannot synthesize. You need a different amount of each of those 9 essential amino acids (EAAs), and dietary proteins are themselves made of different combinations of amino acids. You should therefore take into consideration not just your total protein intake but also your intake of specific amino acids.
Everything you need to know about whey protein
Whey protein is far more complex than you'd think - supplement companies are always trying to pull a fast one over you with legal loopholes and proprietary blends.
Our Definitive Guide to Whey Protein breaks down everything you need to know about whey protein so you can buy the best whey protein for you.
4. Your body is a protein-recycling factory


Getting enough protein is crucial to properly balance periods of fasting and feeding. When fasting, needed amino acids are supplied primarily by the breakdown of your skeletal muscles. When muscle-protein breakdown exceeds synthesis over the long term, muscle loss inevitably results.
5. Protein is the only pragmatically essential macronutrient
A dietary protein deficiency is very possible even in people whose caloric intake is sufficient. The protein-sparing modified fast, in which only protein is consumed, was designed specifically to mimic starvation and promote rapid fat loss without health issues and with minimal loss of muscle mass.
Quickly and easy calculate your optimal daily intake with our protein intake calculator.
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