For decades, fat was the enemy; today, there’s a new scapegoat: people say carbs are bad for you. Vilifying carbs and insulin seems to get more popular by the year.

Many people believe that the popular glycemic index and the lesser-known insulin index rank foods by their “unhealthiness”. Yet the available research shows that low-glycemic diets, when compared to higher-glycemic diets, have either no effect or only modest beneficial effects on metabolic syndrome factors, even in diabetics. Furthermore, a low-glycemic diet doesn’t always lead to better glycemic control than do other diet patterns.

Similarly, the carbohydrate-insulin model of obesity, which theorizes that obesity is caused by carbs and the insulin response they evoke, is not well-supported by the evidence.

In 2017, a meta-analysis of 32 controlled feeding studies was published. Some of those studies were metabolic ward studies and some were free-living studies, but in each case, meals were provided by the researchers, who wished to ensure that each diet would provide specific amounts of calories and nutrients (within each study, the diets were equal in calories and protein but not in fat and carbs).

So what were the results? Low-fat diets resulted in greater fat loss (by an average of 16 grams per day) and greater energy expenditure (by an average of 26 Calories per day). This would give low-fat diets a fat-loss advantage, though one “so small as to be physiologically meaningless”.

These results are consistent with those of long-term, free-living, randomized controlled trials designed to test a diet’s real-world effectiveness (meaning that the participants were given instructions but left to prepare their own meals). Meta-analyses show that keto, low-carb, and higher-carb diets lead to similar weight loss.

Eating less carbohydrate (especially processed carbs) can be helpful if it helps you eat healthier. But if cutting carbs makes you eat worse or feel worse, or if you can’t stick with the diet, you should consider other options. If you wish to lose weight, what matters is not to replace fat by carbs or carbs by fat, but to end most days on a caloric deficit.