Strategies to Counter Weight Loss-Induced Reductions in Metabolic Rate

Intermittent normobaric hypoxia alters substrate partitioning and muscle oxygenation in individuals with obesity: implications for fat burning

This single-blind, crossover study aimed to measure and evaluate the short-term metabolic responses to continuous and intermittent hypoxic patterns in individuals with obesity. Indirect calorimetry was used to quantify changes in resting metabolic rate (RMR), carbohydrate (CHOox, %CHO), and fat oxidation (FATox, %FAT) in nine individuals with obesity pre and post: 1) breathing normoxic air [normoxic sham control (NS-control)], 2) breathing continuous hypoxia (CH), or 3) breathing intermittent hypoxia (IH). A mean peripheral oxygen saturation ([Formula: see text]) of 80-85% was achieved over a total of 45 min of hypoxia. Throughout each intervention, pulmonary gas exchanges, oxygen consumption (V̇o2) carbon dioxide production (V̇co2), and deoxyhemoglobin concentration (Δ[HHb]) in the vastus lateralis were measured. Both RMR and CHOox measured pre- and postinterventions were unchanged following each treatment: NS-control, CH, or IH (all P > 0.05). Conversely, a significant increase in FATox was evident between pre- and post-IH (+44%, P = 0.048). Although the mean Δ[HHb] values significantly increased during both IH and CH (P < 0.05), the greatest zenith of Δ[HHb] was achieved in IH compared with CH (P = 0.002). Furthermore, there was a positive correlation between Δ[HHb] and the shift in FATox measured pre- and postintervention. It is suggested that during IH, the increased bouts of muscle hypoxia, revealed by elevated Δ[HHb], coupled with cyclic periods of excess posthypoxia oxygen consumption (EPHOC, inherent to the intermittent pattern) played a significant role in driving the increase in FATox post-IH.

Metabolic Flexibility and Its Impact on Health Outcomes

A metabolically flexible state exists when there is a rapid switch between glucose and fatty acids during the transition between the fed and fasting state. This flexibility in fuel choice serves to prevent hyperglycemia following a meal and simultaneously ensures an adequate amount of blood glucose is available for delivery to the brain and exclusively glycolytic tissues during fasting. The modern era is characterized by chronic overnutrition in which a mixture of fuels is delivered to the mitochondria in an unabated manner thereby uncoupling the feast and famine situation. The continuous influx of fuel leads to accumulation of reducing equivalents in the mitochondria and an increase in the mitochondrial membrane potential. These changes create a microenvironment fostering the generation of reactive oxygen species and other metabolites leading to deleterious protein modification, cell injury, and ultimately clinical disease. Insulin resistance may also play a primary role in this deleterious effect. The imbalance between mitochondrial energy delivery and use is made worse with a sedentary lifestyle. Maneuvers that restore energy balance across the mitochondria activate pathways that remove or repair damaged molecules and restore the plasticity characteristic of normal energy metabolism. Readily available strategies to maintain energy balance across the mitochondria include exercise, various forms of caloric restriction, administration of sodium-glucose cotransporter-2 inhibitors, cold exposure, and hypobaric hypoxia.

Comparison of Beinaglutide Versus Metformin for Weight Loss in Overweight and Obese Non-diabetic Patients

PURPOSE

We compared the efficacy and safety of beinaglutide, a glucagon-like peptide-1 (GLP-1) analogue with metformin in lowering the bodyweight of patients who were overweight/obese and non-diabetic.

PATIENTS AND METHODS

Seventy-eight non-diabetic patients were randomly selected and beinaglutide or metformin was administered for 12 weeks. The primary endpoints were changes in body weight and the proportions of patients who lost≥5 and≥10% of their baseline body weights.

RESULTS

A total of 64 patients completed the study; patients in the beinaglutide group exhibited more bodyweight loss than those in the metformin group [(9.5±0.8%; 9.1±0.9 kg) and (5.1±0.9%; 4.5±0.8 kg), respectively, corresponding to a difference of approximately 4.5 kg (95% confidence interval, 2.2-6.9 kg; P<0.01)]. In the beinaglutide group, 90.6 and 40.6% of the patients lost≥5 and≥10% of their body weight, respectively, whereas, in the metformin group, these rates were 46.9 and 12.5%, respectively (P<0.01 and P<0.05). Weight loss following beinaglutide treatment mainly resulted from the loss of fat mass. Compared to metformin, beinaglutide induced a greater decrease in the body mass index, weight circumference, percent body fat, and body fat mass (total, trunk, limb, android, and gynoid). Additionally, beinaglutide decreased serum insulin levels and ameliorated insulin resistance.

CONCLUSIONS

Beinaglutide is more efficient than metformin at reducing weight and fat mass in patients who are overweight/obese and non-diabetic. Beinaglutide may be a useful therapeutic option for overweight/obesity control in the Chinese population.

Hypoxia, energy balance, and obesity: An update

Because of the enduring rise in the prevalence of obesity worldwide, there is continued interest in hypoxia as a mechanism underlying the pathophysiology of obesity and its comorbidities and as a potential therapeutic adjunct for the management of the disease. Lifelong exposure to altitude is accompanied by a lower risk for obesity, whereas altitude sojourns are generally associated with a loss of body mass. A negative energy balance upon exposure to hypoxia can be due to a combination of changes in determinants of energy expenditure (resting metabolic rate and physical activity energy expenditure) and energy intake (appetite). Over the past 15 years, the potential therapeutic interest of hypobaric or normobaric hypoxic exposure in individuals with obesity-to lower body mass and improve health status-has become an active field of research. Various protocols have been implemented, using actual altitude sojourns or intermittent normobaric hypoxic exposures, at rest or in association with physical activity. Although several studies suggest benefits on body mass and cardiovascular and metabolic variables, further investigations are required before recommending hypoxic exposure in obesity management programs. Future studies should also better clarify the effects of hypoxia on appetite, the intestinal microbiota, and finally on overall energy balance.