Interindividual variability in weight loss in the treatment of obesity

The metabolic consequences of 'yo-yo' dieting are markedly influenced by genetic diversity

BACKGROUND

Weight loss can improve the metabolic complications of obesity. However, it is unclear whether insulin resistance persists despite weight loss and whether any protective benefits are preserved following weight regain (weight cycling). The impact of genetic background on weight cycling is undocumented. We aimed to investigate the effects of weight loss and weight cycling on metabolic outcomes and sought to clarify the role of genetics in this relationship.

METHOD

Both C57BL/6 J and genetically heterogeneous Diversity Outbred Australia (DOz) mice were alternately fed high fat Western-style diet (WD) and a chow diet at 8-week intervals. Metabolic measures including body composition, glucose tolerance, pancreatic beta cell activity, liver lipid levels and adipose tissue insulin sensitivity were determined.

RESULTS

After diet switch from WD (8-week) to chow (8-week), C57BL/6 J mice displayed a rapid normalisation of body weight, adiposity, hyperinsulinemia, liver lipid levels and glucose uptake into adipose tissue comparable to chow-fed controls. In response to the same dietary intervention, genetically diverse DOz mice conversely maintained significantly higher fat mass and insulin levels compared to chow-fed controls and exhibited much more profound interindividual variability than C57BL/6 J mice. Weight cycled (WC) animals were re-exposed to WD (8-week) and compared to age-matched controls fed 8-week WD for the first time (LOb). In C57BL/6 J but not DOz mice, WC animals had significantly higher blood insulin levels than LOb controls. All WC animals exhibited significantly greater beta cell activity than LOb controls despite similar fat mass, glucose tolerance, liver lipid levels and insulin-stimulated glucose uptake in adipose tissue.

CONCLUSION

Following weight loss, metabolic outcomes return to baseline in C57BL/6 J mice with obesity. However, genetic diversity significantly impacts this response. A period of weight loss does not provide lasting benefits after weight regain, and weight cycling is detrimental and associated with hyperinsulinemia and elevated basal insulin secretion.

Weight loss induced by a hypocaloric diet with or without fish oil supplementation re-established iron and omega-3 fatty acid homeostasis in middle-aged women with obesity: A post-hoc analysis of a randomized controlled trial

OBJECTIVE

Middle-aged women with obesity are at increased risk of iron overload and iron disorder is known to disrupt n-3 polyunsaturated fatty acid homeostasis. We evaluated relationships between pretreatment hemoglobin and n-3 polyunsaturated fatty acid levels, and tested whether pretreatment hemoglobin contributed to inter-individual variability in weight loss with special focus on changes in body weight, iron and n-3 polyunsaturated fatty acid profiles.

STUDY DESIGN

117 middle and older aged women with obesity and more than two metabolic abnormalities were randomized to a 12-week hypocaloric diet without or with fish oil supplementation. Blood iron biomarker and erythrocyte membrane phospholipid profiles were evaluated.

MAIN OUTCOME

The absolute change from baseline to week 12 in serum iron and erythrocyte n-3 polyunsaturated fatty acid levels according to pretreatment hemoglobin tertiles and fish oil supplementation.

RESULTS

A Pearson correlation analysis showed that pretreatment hemoglobin levels were negatively correlated with linoleic acid (r = -0.231), α-linoleic acid (r = -0.279), and n-3 polyunsaturated fatty acid (r = -0.217) (all p < 0.05). Dietary weight loss markedly enhanced erythrocyte membrane lipids of linoleic acid, α-linoleic acid, and n-6 and n-3 polyunsaturated fatty acid only in those women with the highest pretreatment hemoglobin levels (tertile 3) (all p < 0.05). Fish oil supplementation increased bioavailable iron in women with moderate pretreatment hemoglobin levels (tertile 2) (p < 0.05) and, to a lesser extent, prevented a reduction in circulating iron in those with the lowest hemoglobin levels (tertile 1).

CONCLUSION

Dietary weight loss is an effective treatment program to manage obesity-related iron and n-3 polyunsaturated fatty acid disorders, particularly for middle-aged women with obesity and iron overload.

Pharmacologic Management of Obesity after Liver Transplantation: A Critical Review

Post liver transplant obesity is associated with the development of metabolic disorders such as diabetes mellitus and nonalcoholic fatty liver disease and is a strong predictor of post-transplant mortality. Anti-obesity pharmacotherapy could serve as an effective adjunct to lifestyle modification in the post-transplant setting. Currently, utilization of anti-obesity medication in post liver transplant patients is limited by scarce data on their efficacy and safety in the post-transplant setting. Newer classes of anti-obesity medications, including the glucagon-like peptide 1 agonists (GLP-1) do not only help with weight loss but are effective anti-diabetic agents and are in further development for their potential hepatoprotective and renoprotective effects and reduction in cardiovascular risk. The objective of this manuscript was to critically review the efficacy and safety of anti-obesity pharmacotherapy in post-liver transplant patients.

Understanding heterogeneity of responses to, and optimizing clinical efficacy of, exercise training in older adults: NIH NIA Workshop summary

Exercise is a cornerstone of preventive medicine and a promising strategy to intervene on the biology of aging. Variation in the response to exercise is a widely accepted concept that dates back to the 1980s with classic genetic studies identifying sequence variations as modifiers of the VO₂max response to training. Since that time, the literature of exercise response variance has been populated with retrospective analyses of existing datasets that are limited by a lack of statistical power from technical error of the measurements and small sample sizes, as well as diffuse outcomes, very few of which have included older adults. Prospective studies that are appropriately designed to interrogate exercise response variation in key outcomes identified a priori and inclusive of individuals over the age of 70 are long overdue. Understanding the underlying intrinsic (e.g., genetics and epigenetics) and extrinsic (e.g., medication use, diet, chronic disease) factors that determine robust versus poor responses to various exercise factors will be used to improve exercise prescription to target the pillars of aging and optimize the clinical efficacy of exercise training in older adults. This review summarizes the proceedings of the NIA-sponsored workshop entitled, "Understanding Heterogeneity of Responses to, and Optimizing Clinical Efficacy of, Exercise Training in Older Adults" and highlights the importance and current state of exercise response variation research, particularly in older adults, prevailing challenges, and future directions.