Here’s why zero calorie sodas can still lead to weight gain
Q: Is it true that zero calorie sodas don’t help you lose weight?
A: Switching from high calorie to zero calorie drinks could help you lose weight if the rest of your diet remains unchanged. But research suggests that zero calories drinks are not a reliable way to lose weight and might even lead to weight gain.
Here are some reasons why. Artificially sweetened diet sodas may create a craving for sweet, high-calorie foods. So, even as calorie counts drop from zero-calorie sodas, consumption of other foods and drinks might add back even more. The brain’s “turn-off” switch for hunger might be affected by artificial sweeteners. The hunger hormone, ghrelin, may rise in people drinking carbonated beverages (including zero-calorie drinks).
A 2017 study of humans and rats supports the idea that ghrelin may rise and increase hunger after drinking carbonated beverages. In this study, male rats were given one of four drinks over one year: water, a regular carbonated drink, a regular carbonated drink that had been allowed to go flat, or a diet carbonated drink. The rats drinking a carbonated beverage (regular or diet) ate more food and gained more weight than rats drinking water or flat soda. And the amount of ghrelin in the rats’ stomach tissue was higher after exposure to carbonated beverages compared with non-carbonated drinks.
Twenty young men were also studied. They drank five different drinks, one at each sitting over a one-month period. The drinks included water, regular soda, regular soda that had gone flat, diet soda or carbonated water. Soon after, their blood ghrelin levels were measured. After drinking any carbonated beverage (regular soda, diet soda or carbonated water), ghrelin levels rose to higher levels than after drinking water or flat soda. Although this study did not assess food intake or weight changes after drinking different types of beverages, the increased ghrelin levels after carbonated beverage consumption make it plausible that these drinks could lead to hunger, increased food consumption, and weight gain.
Given these findings, you may want to go with plain water, unsweetened tea or fruit-infused water rather than zero calorie carbonated beverages. But, for many, water is not the most appealing choice. If you prefer to drink soda every day, it makes sense to switch from regular to a zero or low-calorie alternative while keeping an eye on the rest of your diet and your weight.
Stay tuned for future research assessing the health effects of a range of low-calorie beverages. While it’s good to have choices, it’s also good to know the pros and cons of each one.
(Robert H. Shmerling, M.D., is a senior faculty editor at Harvard Health Publishing and corresponding member of the Faculty of Medicine, Harvard Medical School. For additional consumer health information, please visit www.health.harvard.edu.)
