Does sugar make you fat?

Not more than any other calorie. When trials swapped sugar for other carbs and kept the calories the same, weight didn’t change. Sugar matters because it’s easy to eat a lot of it without feeling full. Cutting it usually means eating less overall, and that’s where the fat loss comes from.

Why people think it’s special

Sugar gets blamed for switching the body into fat storage through insulin. That story falls apart in careful feeding studies, which we cover in does insulin make you store fat. The simpler problem is that sugar comes in foods that are easy to keep eating.

Sugar is like a subscription you forgot you signed up for. Each charge is small. You only notice when you check the statement.

What the trials found

A 2013 review pooled trials in adults eating freely:

So the effect came through the calories, not through anything sugar does on its own.

The same pattern shows in a 2019 NIH study. 20 adults lived in a clinic for a month and ate as much as they wanted of an ultra-processed diet for two weeks and an unprocessed one for two weeks. On the processed food, they ate about 500 more calories a day and gained about 2 pounds (0.9 kg). On the unprocessed food they lost about the same.

What to do

• Start with sweet drinks. A soda or a sweet coffee is calories with no food attached.
• Keep fruit. The sugar in whole fruit comes packed with fiber and water.
• Watch packaged snacks and desserts that are easy to finish without noticing.