Targeting skeletal muscle mitochondrial health in obesity.

Metabolic demands of skeletal muscle are substantial and are characterized normally as highly flexible and with a large dynamic range. Skeletal muscle composition (e.g., fiber type and mitochondrial content) and metabolism (e.g., capacity to switch between fatty acid and glucose substrates) are altered in obesity, with some changes proceeding and some following the development of the disease. Nonetheless, there are marked interindividual differences in skeletal muscle composition and metabolism in obesity, some of which have been associated with obesity risk and weight loss capacity. In this review, we discuss related molecular mechanisms and how current and novel treatment strategies may enhance weight loss capacity, particularly in diet-resistant obesity.

Derivation and validation of the Ottawa weight loss prediction model for patients on a low-calorie diet.

Accurate weight predictions are essential for weight management program patients. The freely available National Institutes of Health Body Weight Planner (NIH-BWP) returns expected weights over time but overestimates weight when patients consume a low-calorie diet. This study sought to increase the accuracy of NIH-BWP predicted weights for people on low-calorie diets. People enrolled in a weight management program were included if they received meal replacements with defined caloric content for the 3 months of the weight loss phase of the program. The Ottawa Weight Loss Prediction Model (OWL-PM) modelled the relative difference between observed and NIH-BWP predicted weights using longitudinal analysis methods based on patient factors. OWL-PM was externally validated. 1761 people were included (mean age 46 years, 73.3% women) with a mean (SD) baseline weight in pounds and body mass index of 271.9 (55.6) and 43.9 (7.4), respectively. At the end of the program's weight loss phase, people lost a median (IQR) of 17.1% (14.8-19.5) of their baseline weight. Observed weight relative to NIH-BWP predicted weights had a median value of - 4.9% but ranged from - 32.1% to + 28.5%. After adjustment, weight overestimation by NIH-BWP was most pronounced in male patients, people without diabetes and with increased observation time. OWL-PM returned expected weights at 3 months that were significantly more accurate than those from NIH-BWP alone (mean difference observed vs. expected [95% CI] 6.7lbs [6.4-7.0] vs. 12.6lbs [12.1-13.0]). In the external validation cohort (n = 106), OWL-PM was significantly more accurate than NIH-BWP (mean squared error 24.3 vs. 40.0, p = 0.0018). OWL-PM incorporated patient-level covariates to significantly increase weight prediction accuracy of NIH-BWP in patients consuming a low-calorie diet.

Exercise training enhances muscle mitochondrial metabolism in diet-resistant obesity.

BACKGROUND: Current paradigms for predicting weight loss in response to energy restriction have general validity but a subset of individuals fail to respond adequately despite documented diet adherence. Patients in the bottom 20% for rate of weight loss following a hypocaloric diet (diet-resistant) have been found to have less type I muscle fibres and lower skeletal muscle mitochondrial function, leading to the hypothesis that physical exercise may be an effective treatment when diet alone is inadequate. In this study, we aimed to assess the efficacy of exercise training on mitochondrial function in women with obesity with a documented history of minimal diet-induced weight loss. METHODS: From over 5000 patient records, 228 files were reviewed to identify baseline characteristics of weight loss response from women with obesity who were previously classified in the top or bottom 20% quintiles based on rate of weight loss in the first 6 weeks during which a 900 kcal/day meal replacement was consumed. A subset of 20 women with obesity were identified based on diet-resistance (n=10) and diet sensitivity (n=10) to undergo a 6-week supervised, progressive, combined aerobic and resistance exercise intervention. FINDINGS: Diet-sensitive women had lower baseline adiposity, higher fasting insulin and triglycerides, and a greater number of ATP-III criteria for metabolic syndrome. Conversely in diet-resistant women, the exercise intervention improved body composition, skeletal muscle mitochondrial content and metabolism, with minimal effects in diet-sensitive women. In-depth analyses of muscle metabolomes revealed distinct group- and intervention- differences, including lower serine-associated sphingolipid synthesis in diet-resistant women following exercise training. INTERPRETATION: Exercise preferentially enhances skeletal muscle metabolism and improves body composition in women with a history of minimal diet-induced weight loss. These clinical and metabolic mechanism insights move the field towards better personalised approaches for the treatment of distinct obesity phenotypes. FUNDING: Canadian Institutes of Health Research (CIHR-INMD and FDN-143278; CAN-163902; CIHR PJT-148634).

Effects on Diabetes Medications, Weight and Glycated Hemoglobin Among Adult Patients With Obesity and Type 2 Diabetes: 6-Month Observations From a Full Meal Replacement, Low-Calorie Diet Weight Management Program.

OBJECTIVES: A 6-month weight-management program with full meal replacement, low-calorie diet (full MR-LCD) (900 kcal/day for 6 to 12 weeks) follows a protocol for patients with diabetes for decreasing or discontinuing weight-gaining diabetes medications first (Group WG) and then titrating weight-neutral medications (Group WN). METHODS: This is a retrospective cohort study (1992 to 2009) of weight, glycemic control and diabetes medications changes in 317 patients with obesity and type 2 diabetes who were taking medications. RESULTS: Group WG and Group WN were similar at baseline, except that glycated hemoglobin (A1C) levels were significantly lower in Group WN (7.5% vs. 6.6%; p<0.001). At 6 months, both groups had lost 16% of their weight, and the decreases or discontinuations of medications were 92.1% sulfonureas, 86.5% insulins, 78.8% thiazolidinediones, 77.8% alpha-glucosidase inhibitors, 50% meglitinides, 33.3% dipeptidyl peptidase-4 (DPP-4) inhibitors and 32.8% metformin. At 6 months, compared with baseline, A1C levels improved in Group WG and Group WN (6-month A1C levels 6.7% and 5.8%, respectively; p<0.0001), and Group WN had significantly better A1C levels than Group WG. At 6 months, 30% of patients were no longer taking diabetes medications and had significantly better percentages of weight loss compared with those taking medications (18.6% vs. 16%; p=0.002); both groups had improved glycemic control at 6 months (A1C 6.0% vs. A1C 6.6%; NS). CONCLUSIONS: In patients with obesity and type 2 diabetes taking medications, a full MR-LCD program appears to be safe and includes improvement in A1C levels. At 6 months, the percentage of weight loss can be significantly better in patients who no longer require diabetes medications, and A1C levels are best controlled in patients who are on WN medications.

Smoking status and sex as indicators of differences in 2582 obese patients presenting for weight management.

BACKGROUND: Smoking remains the most common preventable cause of death. Very little tobacco exposure can increase cardiovascular disease risk. The relationship between smoking, sex, and weight remains unclear. METHODS: Between September 1992 and June 2007, 2582 consenting patients starting the Ottawa Hospital Weight Management program were grouped by sex and smoking status. "Former smokers" (771 females, 312 males) had quit for at least 1 year. "Smokers" (135 females, 54 males) smoked > 9 cigarettes daily. There were 979 females and 331 males who never smoked. Using SAS 9.2 statistical software, the prevalence of coronary artery disease (CAD), type 2 diabetes (T2DM), major depressive disorder (MDD), and medication use among the groups was compared (Chi-square [χ(2)]). Anthropometric measurements, lipid, glucose and thyroid levels were compared using analysis of variance (ANOVA). Interactions were assessed using 2-way ANOVA analysis for continuous data, and logistic regression for discrete data. RESULTS: Smokers were more likely to have MDD (χ(2)), lower high-density lipoprotein levels and higher triglyceride levels than other groups. Former smokers had a greater prevalence of CAD, T2DM on pharmacotherapy, and impaired fasting glucose than other groups. They were also more likely to be taking lipid-lowering agents and antihypertensives (χ(2)). Never smokers had less MDD, CAD, and were less likely to be on antidepressants than the other groups. Males were more likely to have CAD and T2DM than females. Females were more likely to have MDD than males. Interactions between smoking status and sex were found for age, weight, fasting glucose and thyroid-stimulating hormone levels. CONCLUSION: Obese never smokers suffer from the fewest chronic diseases. Obese former smokers have a greater prevalence of CAD, T2DM on pharmacotherapy, and impaired fasting glucose than other groups. Thus, clinicians and researchers should avoid combining former smokers with never smokers as "nonsmokers" in research and treatment decisions. The results of this study call for a longitudinal study comparing these groups over the weight management program.