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Why are we getting Fat? It’s the Insulin, Stupid.

The Body Fat Thermometer — part 8

Dr. Jason Fung
8 min readMar 7, 2024

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The body regulates how much fat it carries, much like a thermostat. (start with part 1 of series). Gaining weight is the same as increasing the body fat thermostat. What moves it up or down? In simpler terms — why do we get fat?

Was it lack of exercise? No. (see Exercise is pretty Meh).

Was it simply ‘too many calories’? No. (see The Overfeeding paradox). The energy balance equation ‘Body Fat = Calories In — Calories Out’ only describes the problem. It doesn’t tell us how to solve it. Eating less causes the body to burn fewer calories, so that simplistic and ineffective advice to simply ‘Eat Less’ almost never works (see Eat Less, Burn Less).

Think about an analogous ‘Money Balance Equation’ Wealth = Money In — Money Out. This is obviously true, but doesn’t tell you anything about how to get wealthy. Advice to ‘just make more money’ is not useful, in the way that ‘just eat less’ is not useful.

The answer might be for example, ‘study hard, work hard’, to which less bright people might answer ‘but it’s all about money in vs money out, not working hard’. This is analogous to those people that constantly argue, incorrectly, that ‘it’s just about the calories’. It’s not.

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Dr. Jason Fung
Dr. Jason Fung

Written by Dr. Jason Fung

Nephrologist. New York Times best selling author. Interest in type 2 diabetes reversal and intermittent fasting. Founder www.TheFastingMethod.com.

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