Alternate-day fasting, in which people restrict intake to 500 calories one day and eat whatever they want the next, results in successful weight loss with no adverse effects on bone health, according to new research.

"I have been running human trials in alternate-day fasting for about 10 years," said researcher Krista Varady, PhD, from the University of Illinois at Chicago. "People can lose about 1 to 3 pounds a week, so it results in good weight loss."

"Nice reductions in heart disease risk parameters, like LDL cholesterol and triglycerides, and increases in HDL cholesterol" have been demonstrated, she told Medscape Medical News. In addition, "some diabetes protective effects" have been seen, "where insulin levels and insulin resistance go down."

"What we did not know was whether the diet would have adverse effects on bone health," Dr Varady said at the North American Menopause Society 2016 Annual Meeting in Orlando.

Dr Krista Varady

To examine that issue, Dr Varady randomly assigned 100 obese patients to alternate-day fasting, caloric restriction, or no dietary intervention (control group) for 6 months.

The reduction in body weight was significantly better in the fasting and restriction groups than in the control group.

Table. Percent of Body Mass Lost Over 6 Months

Group Body Mass Lost, % P Value Alternate-day fasting 7.8 <.001 Caloric restriction 8.8 <.001 Control 1.0 ns

There were also significant reductions in fat mass in the fasting and restriction groups, compared with the control group.

Levels of leptin decreased by 50% (P < .05) in the caloric-restriction group, compared with the control group, and levels of insulin-like growth factor-1 increased by 11% (P < .05). Both levels remained unchanged in the fasting group.

There were no changes in lean mass, circulating osteocalcin, circulating bone alkaline phosphatase, total bone mineral density, or C-terminal telopeptide type 1 collagen in the three groups.

"It doesn't seem that, as a result of these diets, your body starts breaking down bone. That's a null finding, but a really good null finding," Dr Varady reported.

The Diet for Postmenopausal Women?

There are "some really interesting differences between premenopausal women and postmenopausal women with the alternate-day fasting diet," she pointed out.

"Postmenopausal women do way better on it. They lost twice the amount of weight as the premenopausal women," she reported. In fact, premenopausal women lost 7% to 8% of their body weight with alternate-day fasting, whereas postmenopausal women lost about 30%.

It is not clear why "postmenopausal women did so much better," Dr Varady acknowledged. It could be that "most postmenopausal women just know what kind of diet works for them at that age in their life, and that younger women are still experimenting with different diets."

"This trial adds to a growing body of evidence showing that alternate-day fasting is a safe and effective dietary intervention for weight loss in obese individuals," said Pauline Maki, PhD, professor of psychiatry and psychology at the University of Illinois at Chicago, who was not involved in the study.

"It builds on work showing compelling cardiovascular benefits," Dr Maki told Medscape Medical News.

This study was supported, in part, by grant funding from Pharmavite LLC. Dr Varady has written a book for the general public called The Every Other Day Diet. Dr Maki has disclosed no relevant financial relationships.

North American Menopause Society (NAMS) 2016 Annual Meeting. Presented October 8, 2016.