Obesity is a major global health problem and predisposes individuals to several comorbidities that can affect life expectancy. Interventions based on lifestyle modification (for example, improved diet and exercise) are integral components in the management of obesity. However, although weight loss can be achieved through dietary restriction and/or increased physical activity, over the long term many individuals regain weight. The aim of this article is to review the research into the processes and mechanisms that underpin weight regain after weight loss and comment on future strategies to address them. Maintenance of body weight is regulated by the interaction of a number of processes, encompassing homoeostatic, environmental and behavioural factors. In homoeostatic regulation, the hypothalamus has a central role in integrating signals regarding food intake, energy balance and body weight, while an ‘obesogenic’ environment and behavioural patterns exert effects on the amount and type of food intake and physical activity. The roles of other environmental factors are also now being considered, including sleep debt and iatrogenic effects of medications, many of which warrant further investigation. Unfortunately, physiological adaptations to weight loss favour weight regain. These changes include perturbations in the levels of circulating appetite-related hormones and energy homoeostasis, in addition to alterations in nutrient metabolism and subjective appetite. To maintain weight loss, individuals must adhere to behaviours that counteract physiological adaptations and other factors favouring weight regain. It is difficult to overcome physiology with behaviour. Weight loss medications and surgery change the physiology of body weight regulation and are the best chance for long-term success. An increased understanding of the physiology of weight loss and regain will underpin the development of future strategies to support overweight and obese individuals in their efforts to achieve and maintain weight loss.

This review examines the effect of β-glucan, the viscous soluble fiber in oats, on satiety. A literature search for studies that examined delivery of the fiber in whole foods or as an extract was conducted. Viscosity interferes with the peristaltic mixing process in the small intestine to impede digestion and absorption of nutrients, which precipitates satiety signals. From measurements of the physicochemical and rheological properties of β-glucan, it appears that viscosity plays a key role in modulating satiety. However, the lack of standardized methods to measure viscosity and the inherent nature of appetite make it difficult to pinpoint the reasons for inconsistent results of the effects of oats on satiety. Nevertheless, the majority of the evidence suggests that oat β-glucan has a positive effect on perceptions of satiety.

Context: The efficacy of current centrally acting obesity pharmacotherapies is limited by compensatory mechanisms that mitigate weight loss. Objective: Our objective was to determine whether opioid receptor antagonism (naltrexone) plus pro-opiomelanocortin activation (bupropion) causes greater weight loss than placebo or monotherapy. Design/Setting: A randomized, placebo- and monotherapy-controlled, double-blind, dose-finding trial was conducted from August 2005 to December 2006 in seven U.S. outpatient clinics. Participants: A total of 419 patients with uncomplicated obesity participated. Interventions: Interventions included 24 wk of sustained-release bupropion (400 mg/d), immediate-release naltrexone (48 mg/d), placebo, and three combination therapy [naltrexone/bupropion (NB)] groups consisting of immediate-release naltrexone, 16, 32, or 48 mg/d, plus sustained-release bupropion (400 mg/d) with a 24-wk extension. A minimal diet and exercise component was also included. Main Outcome Measures: Percent weight change from baseline at wk 24 in the intent-to-treat population for NB48 vs. placebo and monotherapy was assessed. Other measurements included body mass index, waist circumference, fasting lipids, glycemic variables, safety, and tolerability. Results: At wk 24, placebo-subtracted weight loss was −4.62% [95% confidence interval (CI) −6.24 to −2.99; P < 0.001] for NB16, −4.65% (95% CI −6.20 to −3.09; P < 0.001) for NB32, and −3.53% (95% CI −5.15 to −1.90; P < 0.001) for NB48. Weight loss was statistically significant vs. monotherapy for all three NB combinations with the exception of NB48 vs. bupropion. Weight loss with NB continued after wk 24. The most common treatment-emergent adverse event was mild transient nausea. Conclusions: NB caused gradual sustained weight loss over 48 wk; NB32 and NB16 demonstrated greater weight loss in the intent-to-treat population due to lower attrition rates. Further study is needed to demonstrate long-term efficacy and safety of NB.

Objective: This study aims to assess the efficacy and safety of Gelesis100, a novel, nonsystemic, superabsorbent hydrogel to treat overweight or obesity.Methods: The Gelesis Loss Of Weight (GLOW) study was a 24‐week, multicenter, randomized, double‐blind, placebo‐controlled study in patients with BMI ≥ 27 and ≤ 40 kg/m² and fasting plasma glucose ≥ 90 and ≤ 145 mg/dL. The co‐primary end points were placebo‐adjusted weight loss (superiority and 3% margin super‐superiority) and at least 35% of patients in the Gelesis100 group achieving ≥ 5% weight loss.Results: Gelesis100 treatment caused greater weight loss over placebo (6.4% vs. 4.4%, P = 0.0007), achieving 2.1% superiority but not 3% super‐superiority. Importantly, 59% of Gelesis100‐treated patients achieved weight loss of ≥ 5%, and 27% achieved ≥ 10% versus 42% and 15% in the placebo group, respectively. Gelesis100‐treated patients had twice the odds of achieving ≥ 5% and ≥ 10% weight loss versus placebo (adjusted OR: 2.0, P = 0.0008; OR: 2.1, P = 0.0107, respectively), with 5% responders having a mean weight loss of 10.2%. Patients with prediabetes or drug‐naive type 2 diabetes had six times the odds of achieving ≥ 10% weight loss. Gelesis100 treatment had no apparent increased safety risks.Conclusions: Gelesis100 is a promising new nonsystemic therapy for overweight and obesity with a highly desirable safety and tolerability profile.