In people with obesity, a lower respiratory exchange ratio measured while resting and eating normally before losing weight is linked to gaining more weight back after the loss, but this link depends...

We analyzed the available evidence and found that in people with obesity, a lower respiratory exchange ratio measured at rest while eating normally before weight loss is linked to gaining more weight back afterward — but this connection depends on how many total calories the body burns each day [1]. The respiratory exchange ratio tells us what type of fuel the body is using — whether it’s burning mostly fat or mostly carbohydrates — based on the balance of oxygen breathed in and carbon dioxide breathed out. A lower ratio suggests the body is relying more on fat for energy at rest. What we’ve found so far is that people with this pattern tend to regain more weight after losing it, but only when their overall daily calorie burn is considered. We did not find any studies that contradicted this observation. The evidence we’ve reviewed leans toward this relationship being influenced by total energy expenditure, meaning how active a person is or how much their body naturally uses throughout the day may change how strongly this link appears. Not enough evidence exists yet to say whether changing this ratio before weight loss could help prevent regain. Our current analysis shows this is one piece of a larger puzzle involving metabolism, energy balance, and behavior. If you’re working to lose weight and keep it off, paying attention to both how much you move and how your body uses fuel may be more helpful than focusing on one number alone.