Thermic Effect of Food (TEF)

Thermic Effect of Food: what is it?

TEF is one of the smaller components of daily expenditure and the one most often oversold. It does not make a diet, and no food has a negative calorie balance. What it does do is provide one more small, real reason why a higher-protein diet behaves differently from a lower-protein one at the same calorie level, which is a useful thing for a coach to be able to explain accurately.

The thermic cost of each macronutrient

The table below ranks the macronutrients by thermic cost, expressed as a share of the calories in that macronutrient. Published estimates vary with the method used to measure them, and the differences between the macronutrients are the point rather than any precise figure.

Why protein wins on more than TEF

The thermic advantage of protein is real and it is not the main reason coaches prescribe a high protein intake. Protein preserves lean mass in a deficit and is the most satiating macronutrient per calorie. TEF is a third, smaller argument stacked on top of two larger ones.

Presenting it the other way round, as though the thermic effect is why clients should eat more protein, sets up a client to be disappointed when the number turns out to be modest. Lead with muscle retention and fullness; mention TEF as a bonus.

What does not change TEF

Meal frequency does not. TEF scales with how much is eaten, not with how many sittings it is split into, so the advice to eat six small meals to stoke the metabolic fire never had a mechanism behind it. Three meals and six meals of the same composition produce the same total.

Negative-calorie foods do not exist either. Celery and similar foods are very low in calories, and the energy required to digest them does not exceed what they provide. They are useful for volume and fiber, which is a good enough reason to eat them without the myth.

• TEF scales with total intake, not with meal frequency.
• Whole and less processed foods generally carry a slightly higher thermic cost than heavily refined ones.
• No food has a negative net calorie balance.
• It is a small component; never build a plan on it.

Where it actually matters to a coach

TEF explains why two diets at identical calories can produce slightly different results and noticeably different hunger. A high-protein, whole-food diet costs more to process and fills the client up more than an isocaloric low-protein, highly processed one.

It also belongs in any explanation of why calorie targets are estimates. TEF is one of several reasons an estimated TDEE is a hypothesis to be corrected against bodyweight data rather than a measurement to be defended.