In recent years, the ketogenic diet has become increasingly popular with people who want to lose weight quickly. A new study asks whether this dietary pattern works as well in females as it does in males.

Experts originally designed the ketogenic diet, which people often refer to as the keto diet, as a treatment for epilepsy. Today, people more commonly use it to increase weight loss or to help control their type 2 diabetes. The keto diet allows a liberal consumption of fats and an adequate amount of protein but heavily reduces the intake of carbohydrates, such as starch, sugar, and fiber. Usually, the body burns carbohydrates as its primary source of energy. However, if there are none available, it switches to burning stored fats. As part of this process, which is called ketosis, the liver turns fatty acids into molecules called ketone bodies.

Keto sex differences

Although there is evidence that the keto diet might offer some benefits for certain people, there is much debate surrounding this diet and its long-term effects. A recent study brings into question whether the keto diet provides the same benefits for females as it does for males. A new study using mouse models focused on sex differences in relation to the keto diet.

The researchers, who are from the University of Iowa in Iowa City, presented their findings at the ENDO 2019 conference in New Orleans, LA. Senior investigator Dr. E. Dale Abel, PhD, chair of the University of Iowa Department of Internal Medicine explains the issue: "Most studies of the ketogenic diet for weight loss have taken place in small numbers of patients or in only male mice, so sex-based differences in response to this diet are unclear."

To investigate, Dr. Abel and research assistant Jesse Cochran fed male and female mice either a ketogenic diet or a standard diet. The keto diet comprised 75% fat, 3% carbohydrates, and 8% protein by mass, while the control diet consisted of 7% fat, 47% carbohydrates, and 19% protein.

After 15 weeks, the researchers found that the male mice on the keto diet maintained blood glucose control and lost body weight. The female mice, however, gained weight. These female mice also had poorer blood sugar control compared with the female mice that ate a standard diet. According to the authors, "[they] developed impaired glucose tolerance."

Why the difference?

The researchers believe that this stark difference might be due, at least in part, to the primary female sex hormone—estrogen. To investigate, they removed the ovaries of some of the female mice and ran a similar experiment. Doing this changed the results substantially.

Compared with mice that received a control diet, female mice without ovaries that consumed a keto diet showed a decrease in body fat, and they also maintained blood glucose control. In other words, without estrogen, the keto diet worked.

Cochran explains, "This finding suggests that postmenopausal women could potentially experience better weight loss outcomes with the ketogenic diet compared to younger women." However, the researchers make it clear that it is important to speak with a doctor before embarking on the keto diet.

This study is one of very few to investigate potential sex differences in the effectiveness of the keto diet. However, the study used an animal model, so scientists will still need to carry out investigations in humans before we can reach any solid conclusions.