Health Advice



Zero weight loss from zero calorie drinks? Say it ain’t so

Robert H. Shmerling, Harvard Health Blog on

Published in Health & Fitness

But a 2017 study of humans and rats casts doubt on this approach too.

First, the rats: For more than a year, male rats were given one of four drinks: water, a regular carbonated drink, a regular carbonated drink that had been allowed to go flat, or a diet carbonated drink. The regular carbonated beverages had sweetener that wasn’t artificial.

Here’s what the researchers found:

And now, the humans: Twenty male students drank five drinks, one at each sitting during 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.

When students drank any carbonated beverage (regular soda, diet soda, or carbonated water), their ghrelin levels rose to higher levels than when they drank water or flat soda.

Although this study did not assess the students’ 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 might lead to hunger, increased food consumption, and weight gain. And that’s cause for concern.

Why would drinking carbonated beverages encourage your body to release more ghrelin? The study authors speculate that cells in the stomach that are sensitive to pressure respond to the carbon dioxide in carbonated beverages by increasing ghrelin production.

What’s left to drink?

The short answer is easy: water. Unsweetened tea or fruit-infused water are also good alternatives.


It’s worth emphasizing that drinking an occasional regular soda or other carbonated beverage is not hazardous. The question is, what’s your default drink of choice — and what are its possible consequences?

The bottom line

While plain water might be best health-wise, for many it’s not the most appealing choice. If you prefer to drink soda every day, it makes sense to switch from regular to a zero-calorie alternative. A low-calorie carbonated beverage may still be a reasonable choice, as long as you keep an eye on the rest of your diet and your weight.

There’s a real possibility that carbonated beverages may have underappreciated negative effects on appetite and weight. Still, it would be premature to say that we should all give up carbonated beverages lest the obesity epidemic worsen.

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.)

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