The neuropeptide Y-ergic system: potential therapeutic target against bone loss with obesity treatments

Effect of Weight Loss via Severe vs Moderate Energy Restriction on Lean Mass and Body Composition Among Postmenopausal Women With Obesity: The TEMPO Diet Randomized Clinical Trial

IMPORTANCE

Severely energy-restricted diets are the most effective dietary obesity treatment. However, there are concerns regarding potential adverse effects on body composition.

OBJECTIVE

To compare the long-term effects of weight loss via severe vs moderate energy restriction on lean mass and other aspects of body composition.

DESIGN, SETTING, AND PARTICIPANTS

The Type of Energy Manipulation for Promoting Optimum Metabolic Health and Body Composition in Obesity (TEMPO) Diet Trial was a 12-month, single-center, randomized clinical trial. A total of 101 postmenopausal women, aged 45 to 65 years with body mass index (calculated as weight in kilograms divided by height in meters squared) from 30 to 40, who were at least 5 years after menopause, had fewer than 3 hours of structured physical activity per week, and lived in the Sydney metropolitan area of New South Wales, Australia, were recruited between March 2013 and July 2016. Data analysis was conducted between October 2018 and August 2019.

INTERVENTION

Participants were randomized to either 12 months of moderate (25%-35%) energy restriction with a food-based diet (moderate intervention) or 4 months of severe (65%-75%) energy restriction with a total meal replacement diet followed by moderate energy restriction for an additional 8 months (severe intervention). Both interventions had a prescribed protein intake of 1.0 g/kg of actual body weight per day, and physical activity was encouraged but not supervised.

MAIN OUTCOMES AND MEASURES

The primary outcome was whole-body lean mass at 12 months after commencement of intervention. Secondary outcomes were body weight, thigh muscle area and muscle function (strength), bone mineral density, and fat mass and distribution, measured at 0, 4, 6, and 12 months.

RESULTS

A total of 101 postmenopausal women were recruited (mean [SD] age, 58.0 [4.2] years; mean [SD] weight, 90.8 [9.1] kg; mean [SD] body mass index, 34.4 [2.5]). Compared with the moderate group at 12 months, the severe group lost more weight (effect size, -6.6 kg; 95% CI, -8.2 to -5.1 kg), lost more whole-body lean mass (effect size, -1.2 kg; 95% CI, -2.0 to -0.4 kg), and lost more thigh muscle area (effect size, -4.2 cm2; 95% CI, -6.5 to -1.9 cm2). However, decreases in whole-body lean mass and thigh muscle area were proportional to total weight loss, and there was no difference in muscle (handgrip) strength between groups. Total hip bone mineral density (effect size, -0.017 g/cm2; 95% CI, -0.029 to -0.005 g/cm2), whole-body fat mass (effect size, -5.5 kg; 95% CI, -7.1 to -3.9 kg), abdominal subcutaneous adipose tissue (effect size, -1890 cm3; 95% CI, -2560 to -1219 cm3), and visceral adipose tissue (effect size, -1389 cm3; 95% CI, -1748 to -1030 cm3) loss were also greater for the severe group than for the moderate group at 12 months.

CONCLUSIONS AND RELEVANCE

Severe energy restriction had no greater adverse effect on relative whole-body lean mass or handgrip strength compared with moderate energy restriction and was associated with 2-fold greater weight and fat loss over 12 months. However, there was significantly greater loss of total hip bone mineral density with severe vs moderate energy restriction. Therefore, caution is necessary when implementing severe energy restriction in postmenopausal women, particularly those with osteopenia or osteoporosis.

TRIAL REGISTRATION

anzctr.org.au Identifier: 12612000651886.

Effects of obesity treatments on bone mineral density, bone turnover and fracture risk in adults with overweight or obesity

BACKGROUND

New evidence suggests that obesity is deleterious for bone health, and obesity treatments could potentially exacerbate this.

MATERIALS AND METHODS

This narrative review, largely based on recent systematic reviews and meta-analyses, synthesizes the effects on bone of bariatric surgery, weight loss pharmaceuticals and dietary restriction.

RESULTS AND CONCLUSIONS

All three obesity treatments result in statistically significant reductions in hip bone mineral density (BMD) and increases in bone turnover relative to pre-treatment values, with the reductions in hip BMD being strongest for bariatric surgery, notably Roux-en Y gastric bypass (RYGB, 8%-11% of pre-surgical values) and weakest for dietary restriction (1%-1.5% of pre-treatment values). Weight loss pharmaceuticals (orlistat or the glucagon-like peptide-1 receptor agonist, liraglutide) induced no greater changes from pre-treatment values than control, despite greater weight loss. There is suggestive evidence that liraglutide may increase bone mineral content (BMC) - but not BMD - and reduce fracture risk, but more research is required to clarify this. All three obesity treatments have variable effects on spine BMD, probably due to greater measurement error at this site in obesity, suggesting that future research in this field could focus on hip rather than spine BMD. Various mechanisms have been proposed for BMD loss with obesity treatments, notably reduced nutritional intake/absorption and insufficient exercise, and these are potential avenues for protection against bone loss. However, a pressing outstanding question is whether this BMD reduction contributes to increased fracture risk, as has been observed after RYGB, and whether any such increase in fracture risk outweighs the risks of staying obese (unlikely).