Diet soda and weight loss: what the studies say

Is cola zero worse than regular cola? People ask me this in coaching all the time. They are afraid of cravings and of what it will do to the gut. The short version from the data, including a clear summary by Layne Norton, is the opposite of the scare.

Short answer: Diet cola is not worse than regular cola. It is in a better place. When diet sodas replace sugary drinks, people lose weight and metabolic markers improve (PMID 35285920). The claims that cola zero wrecks the gut microbiome, or drives cravings up, have not been confirmed in people.

What the human data show

A randomized, double-blind crossover trial on aspartame found no microbiome change (PMID 33171964). A later review reached the same point: aspartame and acesulfame-K (Ace-K) do not usually affect the human microbiome (PMID 37111090).

On cravings and intake, a meta-analysis found that people who switch from sugary drinks to diet drinks drink less of the sugary kind, and they lose even more weight than people who switch to water (PMID 26365102). Yes: diet cola beats regular cola for this job.

I hear the fear in coaching constantly. When we use the diet version on purpose, usually instead of a sugary soda, it helps people drop fat and keep the day calmer. I do not see a risk in it when the rest of the diet has enough protein and vegetables. Liquid sugar itself is the leak, covered in is sugar bad for weight loss.

What to take from it

• For fat loss: swap sugary drinks for diet drinks. The studies show fewer cravings and better calorie control. Sugary drinks are an easy place to cut added sugar.
• For the gut: nothing confirms that aspartame wrecks the human microbiome. A diet with yogurt and vegetables will do more for digestion and energy than worrying about a diet soda.
• For the long run: diet soda is not a devil. Pair it with movement and sleep. If you have a diagnosis, talk to your doctor. This article is not medical treatment.

Drinks at dinners and events, including the alcoholic ones, are in drinks, dinners and social events. Hunger and sweet cravings on a diet are in cravings and hunger.

Frequently asked questions

Does the aspartame in diet cola wreck the gut microbiome?

The human data do not show that. A randomized, double-blind crossover trial on aspartame found no change. A review reached the same point: aspartame and Ace-K do not usually affect the human microbiome.

Do diet sodas increase a craving for sweet food?

Not in people, on the evidence we have. A meta-analysis found that people who switch from sugary drinks to diet drinks then drink less of the sugary kind.

Is it better to swap a sugary soda for a diet soda, or for water?

In the meta-analysis Norton cites, people who switched from sugary drinks to diet drinks lost even more weight than people who switched to water.

Will diet cola instead of regular cola help me lose fat?

Yes. Swap the sugary drink for the diet one. The studies show fewer cravings and better calorie control. Used on purpose, in place of a sugary soda, it helps fat loss, as long as the rest of the diet has enough protein and vegetables.

Sources, so you can check:

1) PMID 35285920: when diet sodas replace sugary drinks, people lose weight and metabolic health improves

2) PMID 33171964: randomized, double-blind crossover trial, aspartame, no microbiome change

3) PMID 37111090: review, aspartame and acesulfame-K do not usually affect the human microbiome

4) PMID 26365102: meta-analysis, switching from sugary drinks to diet drinks cut sugary intake and produced more weight loss than switching to water

Martin Barna

Online nutrition and fitness coach. Since 2013 I have helped 600+ people lose fat and keep the result. Science, not crash diets.

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This article is for information only. It is not medical advice. If you have a health condition, talk to your doctor.