August 10, 2025

Why sugar doesn’t automatically make you fat

Another myth that you’ve likely heard about sugar is that it makes you gain weight.

Which is technically true – if you eat too much of it. The same goes for literally any food that you can think of.

I could eat nothing but fruit and still put on weight if I eat too much, however this would be insanely hard to do due its low energy density (amount of calories per gram of food).

Likewise, it’s possible to just eat fast food and lose weight. Again this would be really hard to achieve because takeaways are typically very energy dense but it can be done. Obviously, I would not recommend doing this!

It all comes down to energy balance (calories in vs calories out) at the end of the day. Eat above your calorie requirements and you’ll store the remaining energy as muscle or fat, eat below what your body requires and it’ll use some of that stored energy to compensate for the lack of food.

Back to sugar – if it was fattening irrespective of overall calorie intake then surely the prevalence of obesity would correlate with sugar consumption?

As you can see, however, this is not the case. Obesity rates continue to rise despite overall sugar intake decreasing in the last 20+ years.

Similarly to the sugar addiction theory I can understand why people may think that sugar causes weight gain. Processed foods are easy to overeat which, as discussed earlier, is what actually causes people to put on body fat – not an individual ingredient.

This study is a perfect example. Participants were split into two groups – one followed a diet made up on minimally processed foods & the other an ultra-processed diet. They both followed this diet for 2 weeks before switching groups and eating the opposite one for a further 2 weeks. Participants ate 508 calories more per day when in the ultra-processed group despite the meals being matched for calories, energy density, sugar, sodium & macronutrients.

You’ve probably heard at some point that you need to cut out sugar if you want to lose weight. Whilst limiting the amount you eat is probably a good idea, you don’t have to completely eradicate it from your diet to see results.

In this study, women who followed a high-sucrose diet lost just as much weight as women consuming a low-sucrose diet after 6 weeks.

Changes in sugar consumption do appear to have a positive correlation with bodyweight. So if you add sugar to your diet you’re likely to gain a bit of weight & the opposite will occur if you remove it from your diet.

However, the same paper found that when sugar is swapped calorie-for-calorie with other sources of carbohydrate, there is no change in bodyweight. If sugar was fattening then we’d expect to see a decrease in weight once it’s replaced with something else.

I should reiterate that I’m not encouraging you to go and double the amount of sugar you eat just for the sake of it.

Just remember that sugar really isn’t something that should be demonised & can be enjoyed moderately as part of a varied diet!

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