Think a balanced diet is the key to avoiding weight gain? A new study suggests otherwise. Researchers say calories— not the ratio of protein, fat, and carbs— are the main reason we plump up.

In the study, 25 men and women ages 18 to 35 ate about 1,000 extra calories a day (who suckered them into that?) for eight weeks. But nutritional values varied among three groups— some ate a low-protein diet and others ate a normal or high-protein diet. Results showed all participants accumulated about the same amount of body fat, although the low-protein group gained slightly more fat. Study authors conclude excess calories mean extra body fat, regardless of whether those calories come from grilled chicken or Krispy Kremes.

While body fat levels were similar, the low-protein group gained the least amount of weight. But don’t carbo-load just yet— it’s probably because that group lost the most muscle mass. Metabolic rate (the speed at which the body burns calories) also increased slightly for those on the high-protein diet, which may explain why the high-protein group gained less body fat.

When it comes to losing or gaining body fat, this study suggests calories matter most. But protein and other nutrients have important health benefits, so stay away from a 1,000-calorie, Oreo-only diet. Eating more protein helps fill us up, and fiber in fruits and veggies can also help cut calories. So stick to nutritious foods that’ll satisfy us without packing on the calories— and those pesky pounds may stay off for good.

Experts’ Take

We weighed in with our experts, researcher Dr. Douglas Kalman and biologist Jason Edmonds, for their take on the study:

Dr. Douglas Kalman:

“Counting calories alone is insufficient for weight balance… Higher protein intakes correlate with enhanced metabolic rate (calorie burning), so it very well may be that slightly reduced calorie diets that have up to 25 percent calories from protein not only enhance fat free mass (muscle tone), but aid in fat loss.”

Jason Edmonds:

“The authors admit that the overfeeding phase of this study resulted in a daily energy surplus that was in excess of typical real world overeating… This leads me to question whether the results would have been different if the overeating phase contained less than a 40 percent surplus over total energy expenditure for each individual… Perhaps at a lower daily energy surplus, greater protein intake can decrease fat production to some extent.”

In the context of this study, calories mattered more than the amount of protein consumed.  But the study may not be indicative of real-life overeating, and our experts suggest the amount of protein we eat can still affect our weight. Ultimately, this research suggests eating significantly more calories than we expend will lead to weight gain.