A 25 percent calorie restriction over two years by adults who were not obese was linked to better health-related quality of life, according to the results of a randomized clinical trial published online by JAMA Internal Medicine.

Calorie restriction can increase longevity in many species but concerns remain about potential negative effects of calorie restriction in humans.

Corby K. Martin, Ph.D., of the Pennington Biomedical Research Center, Baton Rouge, La., and coauthors tested the effects of calorie restriction on aspects of quality of life that have been speculated to be negatively affected by calorie restriction, including decreased libido, lower stamina, depressed mood and irritability. Their work extends the literature with a study group of nonobese individuals because beneficial effects of calorie restriction on health span (length of time free of disease) increase the possibility that more people will practice calorie restriction.

In this clinical trial conducted at three academic research institutions, 220 men and women with body mass index of 22 to 28 were enrolled and divided almost 2 to 1 into two groups: the larger group was assigned to two years of 25 percent calorie restriction and the other was an ad libitum (their own preference) control group for comparison. The analysis included 218 participants and self-report questionnaires were used to measure mood, quality of life, sleep and sexual function.

Data were collected at baseline, a year and two years. Of the 218 participants, the average age was nearly 38 and 70 percent were women. The calorie restriction group lost an average of 16.7 pounds compared with less than a pound in the control group at year two.

According to the authors, the calorie restriction group, compared with the control group, had improved mood, reduced tension and improved general health and sexual drive and relationship at year two, as well as improved sleep at year one. The bigger weight loss by the calorie restriction participants was associated with increased vigor, less mood disturbance, improved general health and better quality of sleep.

A limitation of the study is its selection of a sample of healthy individuals.

"Calorie restriction among primarily overweight and obese persons has been found to improve QOL [quality of life], sleep and sexual function, and the results of the present study indicate that two years of CR [calorie restriction] is unlikely to negatively affect these factors in healthy adults; rather, CR is likely to provide some improvement," the authors conclude.

"Effect of Calorie Restriction on Mood, Quality of Life, Sleep, and Sexual Function in Healthy Nonobese Adults" Corby K. Martin, PhD1; Manju Bhapkar, MS; Anastassios G. Pittas, MD; Carl F. Pieper, DrPH; Sai Krupa Das, PhD; Donald A. Williamson, PhD1; Tammy Scott, PhD; Leanne M. Redman, PhD; Richard Stein, PhD; Cheryl H. Gilhooly, PhD; Tiffany Stewart, PhD; Lisa Robinson, RD; Susan B. Roberts, PhD ; for the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE) Phase 2 Study Group. JAMA Intern Med. doi:10.1001/jamainternmed.2016.1189. Published online May 02, 2016.

Also available are the related article, "Innovative Self-Regulation Strategies to Reduce Weight Gain in Young Adults; the Study of Novel Approaches to Weight Gain Prevention (SNAP) Randomized Clinical Trial," doi:10.1001/jamainternmed.2016.1236, and the related commentary, "Obesity Management and Prevention; More Questions Than Answers" doi:10.1001/jamainternmed.2016.1211.