Calorie Restriction Improves Mood, Sleep, and Sexual Health in Healthy Adults

Insights from the CALERIE 2 Randomized Clinical Trial

Calorie restriction (CR) has long been associated with longevity and reduced risk of chronic disease in animals, but evidence in healthy, non-obese humans has remained limited. The CALERIE 2 study, a landmark 2-year randomized clinical trial, set out to evaluate the psychological and physiological effects of moderate CR in adults with normal to slightly elevated body mass index (BMI 22–28).

Researchers sought to answer a key question: Can reducing calorie intake improve not just physical health, but also mood, sleep, sexual function, and overall quality of life?

Study Overview

• Participants: 218 healthy, non-obese adults aged 20–50 years (65.6% in the CR group)
• Duration: 2 years
• Intervention: 25% caloric restriction vs. an ad libitum (AL) control group
• Primary Outcomes: Mood, quality of life, sleep, sexual function, and sex hormone levels (men only)
• Methods: Self-report questionnaires, body composition, hormone assays, and correlation analyses

Key Findings

1. Improved Mood and Reduced Tension

Participants in the CR group showed:

• A significant reduction in depression scores (BDI-II: effect size −0.35)
• Decreased tension and mood disturbance (POMS: effect size −0.39)

Notably, men in the CR group reported fewer depressive symptoms compared to men in the AL group, indicating a gender-specific benefit.

2. Better Perceived General Health

Despite already high baseline QOL scores, CR participants reported significant improvements in:

• General health (SF-36: effect size 0.75)
• This reflects a stronger sense of vitality and perceived wellness over 24 months

3. Enhanced Sleep Duration

• While total sleep quality didn’t differ significantly, the CR group maintained sleep duration, whereas the AL group experienced a decline.
• Sleep duration at month 12 favored the CR group (effect size −0.32)

4. Improved Sexual Drive and Relationship Quality

• CR participants reported improved sexual drive and relationship satisfaction after 24 months (effect size 0.35)
• In men, CR was associated with biological changes such as increased SHBG and reduced free testosterone, aligning with improved metabolic markers

5. Weight Loss Correlated with Psychological Gains

Average weight loss in the CR group was 7.6 kg over 24 months

Greater weight loss was linked with:

• Increased vigor
• Better mood
• Improved general health
• Higher sleep quality scores
• Hormonal Insights (Men Only)
• SHBG (Sex Hormone Binding Globulin) increased significantly in the CR group (effect size 1.49 at month 24), which is favorable for metabolic health
• Free testosterone decreased modestly but total testosterone, LH, and FSH remained stable

These results suggest endocrine adaptations rather than disruptions, with possible long-term metabolic benefits

No Evidence of Harm

Despite concerns that long-term CR might impair mood, libido, or vitality, the study found no adverse psychological or hormonal effects in healthy adults. Instead, modest but consistent benefits across multiple domains suggest that CR, when done responsibly, can enhance well-being.

Conclusion

This comprehensive trial indicates that 25% calorie restriction over two years can lead to measurable improvements in mood, sleep, perceived general health, and aspects of sexual function in healthy, non-obese adults. Importantly, the study demonstrated that CR did not negatively affect quality of life or psychological well-being. These findings provide strong evidence that CR may not only extend healthspan, but also enhance day-to-day wellness.

Source:
Martin CK, Bhapkar M, Pittas AG, et al. Effect of Calorie Restriction on Mood, Quality of Life, Sleep, and Sexual Function in Healthy Nonobese Adults: The CALERIE 2 Randomized Clinical Trial. JAMA Intern Med. 2016;176(6):743–752 (https://pmc.ncbi.nlm.nih.gov/articles/PMC4905696/).