So how many calories do we need to eat to gain weight?!

Updated: Dec 1, 2023

Weight – variable…I think what you’re more concerned with is not weight gain, it’s fat gain. I’ve said it one million and one (yep, I’m counting!) times before, the scale weight is affected by FAR more than your body fat levels. What most people are concerned with is their body composition and so whether or not they are gaining fat.

So, let’s look at a review paper by Hall from 2007.

It is often said that a cumulative deficit of 3500Kcal is required to lose a single pound of body weight generally, and the same applies the other way – over eat by 3500 calories and you’ll gain 1lb. And that is OVER eat, not merely eating 3500Kcal.

The study went further and examined the effect that starting body fat levels, lean body mass and starting body weight had on these numbers.

They found that a larger cumulative deficit was needed per pound of weight loss for those with a greater starting body fat. This could explain why men can often lose more weight than women for a given deficit – largely, women have a higher starting body fat than men do!

Over time, more weight is lost in the same energy deficit for those with lower initial body fat levels as they require a lower energy deficit to produce the same amount of weight loss…are we following?

Typically, weight loss will slow over time for a constant diet, confirming what we already know – essentially that energy expenditure tends to decrease as a person gets lighter.

So, one of the takeaways here would be that the 3500Kcal per pound rule that is often banded about may be over-estimated for those with lower body fat levels.

It is likely that there are plenty of other factors play a role in rate of weight loss besides the very few discussed here including things like resistance training or macronutrient composition of diets amongst many others, so don’t get too caught up in the minutia.