Is Yogurt a Diet Food?

Fans claim a variety of benefits from probiotics, including weight loss. Yogurt may be a diet food, but probiotics are not as simple as they’re touted to be.

Americans once thought of yogurt as a spartan breakfast or lunch suitable for a dieting teenage girl or older woman. More recently, yogurt has become the best-known probiotic food, the lead player in a huge and fast-growing business, with recent U.S. sales of more than 9 billion.

Fans claim a variety of benefits from probiotics, including weight loss. The problem is that the word “probiotics” covers a wide variety of bacteria, with different effects. Saying “probiotic” is like saying “European” as if Danes were just like Greeks.

YOU MIGHT ALSO LIKE: The Health Benefits of Kefir

What are probiotics?

The probiotic argument runs like this: you need “friendly” bacteria to rebalance the normal inhabitants of your large intestine or colon, which science shows have been influenced in bad ways by the standard Western diet. Probiotic supplements or food may contain a single strain of bacteria or many, in daily doses of 1 to more than 250 billion organisms.

Lactobacillus bulgaricus and Streptococcus thermophiles are the two bacteria that turn milk (including cow, sheep, and goat milk) into yogurt. The voluntary “Live & Active Cultures” seal from the International Dairy Foods Association (IDFA) is a promise that a refrigerated yogurt contains at least 100 million cultures per gram of those two bacteria at the time of manufacture (10 million for frozen yogurt) — but many may have perished since then.

The Food and Drug Administration has not approved the seal, and the IDFA doesn’t monitor products.

Is yogurt a diet food?

Some people see yogurt as a diet food because it contains calcium. There’s evidence that consuming too little calcium can contribute to obesity, and some research suggests that eating extra dairy and calcium may help you lose weight, though the evidence is slight.

Perhaps the best evidence tying dairy and healthy weight comes from a 2014 analysis of data collected from 3,440 U.S. participants over 17 years.

The volunteers filled out food questionnaires on four occasions and reported on their weight and waist size. Volunteers who ate more than three servings of dairy a day gained less weight and added fewer inches than those who ate less than one. Eating more than three servings a week of yogurt also helped them stay trim.

This study added to the growing body of evidence that standard dieting advice, “Eat less and exercise more,” is too simple. What you eat counts, too, as well as other factors, such as how much you sleep.

It may surprise you to learn that some kinds of lactobacillus promote weight gain in both humans and animals.   

Farmers have been giving animals probiotics to promote weight gain for decades, most commonly Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus fermentum, and Lactobacillus reuteri. Infants and people with diseases causing weight loss have also received various lactobacillus supplements to promote weight gain.

A review of 17 randomized control trials in humans, 51 studies on farm animals, and 14 experimental models concluded that Lactobacillus acidophilus in particular caused significant weight gain in humans. Acidophilus is often included in yogurts touted as especially probiotic, and Greek yogurt, non-dairy yogurt, and kefir, a fermented milk drink.

The same review — and others — have found that a strain called Lactobacillus gasseri can aid weight loss. Gasseri may show up in traditional fermented foods, but it’s not on labels in your supermarket — researchers isolated it from breast milk.

What you can do

Acidophilus may help weight loss, however, if it is combined with particular other strains of lactobacillus.

You may see reliable products emerge as the science develops. In the meantime, if you want to eat yogurt while trying to keep your weight down or lose pounds, it makes sense to stick to ordinary yogurts, if you can find them — or experiment a bit to see what seems to work for you.

Read labels and choose plain or unsweetened yogurt. Although eating yogurt regularly is linked to a reduced risk of weight gain, it is unclear whether simply adding it to your diet helps you lose weight. That said, replacing low-protein, high-calorie snacks with yogurt might help.

To hedge your bets, try a variety of traditional fermented foods rather than eating the same yogurt every day. That will help get more than one culture in your gut.

YOU MIGHT ALSO LIKE: Our Nutrition section