Do obese individuals burn fewer calories?
Obese individuals have traditionally been thought to have a “slow metabolism”.
However, most studies point to the opposite, suggesting that obese individuals have higher total and resting calorie expenditures, compared to non-obese people.
Specifically, the difference was, on average, 360 kcal/day. The difference ranged from 49 kcal/day to 826 kcal/day, depending on the level of obesity, and was highest when severely obese individuals were compared to normal-weight people.
This may be because obese individuals tend to have higher amounts of metabolically active fat-free mass — mainly muscles. When people gain large amounts of fat, they also tend to gain muscle mass to support the additional weight.
Yet, a few studies suggest that resting calorie expenditure may be higher in obese individuals regardless of the higher fat-free mass.
In contrast, a few studies suggest that the rise in calorie expenditure after eating (thermic effect of food) may be lower in obese people, but the evidence is mixed and inconclusive.
Overall, obese people may burn more calories than normal-weight people, suggesting that slow metabolism is not to blame.
Nevertheless, some individuals may burn fewer calories while dieting or fasting, making it harder for them to lose weight.
Bottom Line: Obese individuals tend to burn more calories at rest, compared to normal-weight individuals. Most studies suggest that differences in fat-free mass may explain these findings.