Effects of consuming a high-protein diet with or without soy protein during weight loss and maintenance: a non-inferiority, randomized clinical efficacy trial

OBJECTIVE

This 12-month randomized, non-inferiority clinical trial sought to determine the impact of consuming soy protein as part of an energy-restricted, high-protein diet on weight loss, body composition and cardiometabolic health.

METHODS

Seventy-one adults (58 female) with overweight or obesity (body mass index: 32.9 ± 3.6 kg m-2) were randomly assigned to consume three servings of soy (S) or non-soy (NS) protein foods per day for 12 months. All participants completed a group-based behavioural weight loss program lasting 4 months (M4), and follow-up assessments were completed at month 12 (M12).

RESULTS

Body weight was reduced in both groups at M4 (S: -7.0% ± 5.2%, NS: -7.1% ± 5.7%) and M12 (S: 3.6% ± 5.1%, NS: -4.8% ± 7.3%). Body weight reductions (mean difference [90% confidence interval]) were not different between S and NS at either time point (M4: -0.16% [-1.4, 3.6], P = 0.90; M12: 1.1% [-1.4, 3.6], P = 0.44). Differences in body fat mass loss were not different between S and NS at M4 (0.29 ± 0.84 kg, P = 0.73) or M12 (0.78 ± 1.5 kg, P = 0.59). Weight loss-induced improvements in cholesterol, triglycerides and blood pressure did not differ between S and NS.

CONCLUSION

These results indicate that soy-based protein foods can be effectively incorporated into an energy-restricted, high-protein diet for improving body weight, body composition and cardiometabolic health.

Equivalent reductions in body weight during the Beef WISE Study: beef's role in weight improvement, satisfaction and energy

Objective

The objective of this randomized equivalence trial was to determine the impact of consuming lean beef as part of a high protein (HP) weight‐reducing diet on changes in body weight, body composition and cardiometabolic health.

Methods

A total of 120 adults (99 female) with overweight or obesity (BMI: 35.7 ± 7.0 kg m⁻²) were randomly assigned to consume either a HP diet with ≥4 weekly servings of lean beef (B; n = 60) or a HP diet restricted in all red meats (NB; n = 60) during a 16‐week weight loss intervention.

Results

Body weight was reduced by 7.8 ± 5.9% in B and 7.7 ± 5.5% in NB (p < 0.01 for both). Changes in percent body weight were equivalent between B and NB (mean difference: 0.06%, 90% confidence interval: (−1.7, 1.8)). Fat mass was reduced in both groups (p < 0.01; B: 8.0 ± 0.6 kg, NB: 8.6 ± 0.6 kg), while lean mass was not reduced in either group. Improvements in markers of cardiometabolic health (total cholesterol, low‐density lipoprotein cholesterol, triglycerides and blood pressure) were not different between B and NB.

Conclusion

Results of this study demonstrate that HP diets – either rich or restricted in red meat intakes – are effective for decreasing body weight and improving body composition and cardiometabolic health.

Initial weight loss goals: have they changed and do they matter?

Objective

Nearly 20 years ago, participants in behavioural weight loss programmes reported goals that greatly exceeded the amount of weight typically produced by these programmes. Whether having unrealistic weight loss goals impacts weight loss or attrition is unclear. The intent of the current study was to revisit current weight loss goals and examine whether goals impact outcomes.

Methods

Adults (N = 308, BMI = 33.7 ± 4.2 kg/m²) participated in a 12‐month behavioural weight management programme and completed questionnaires about their goals.

Results

Participants' weight loss goal was 19.8 ± 7.9% of their body weight, and 90.4% selected a goal ≥10%. Weight goals were not associated with weight loss at 3 (p = 0.75) or 12 months (p = 0.47), or from 3 to 12 months (p = 0.55). Weight loss goals were not related to attrition at 3 (p = 0.91) or 12 months (p = 0.86). Participants believed that weight reduction would positively impact their health and psychosocial functioning.

Conclusion

Weight loss goals have decreased, but still greatly exceed what can be expected by most. Unrealistic goals, however, had no impact on weight loss or attrition. These results question the utility of counseling people with obesity to set more realistic weight loss goals, which is typically practiced in behavioural weight management.

International strategies to address obesity

Obesity rates are increasing in most countries throughout the world. The reasons for the increase are complex and involve biological, behavioural and environmental factors. We have unintentionally created environments that encourage over-eating and discourage physical activity. Despite the recognition of the seriousness of obesity to public health, no interventions have been effective in reducing obesity rates on a population basis. Reversing obesity rates within populations will require addressing both individual behaviour and the obesogenic environment. Obesity rates could be reduced by treating affected individuals or by preventing the gradual increase in body weights of the population. Success in long-term obesity treatment is poor and appears to require that large behaviour changes be made and sustained. An alternative approach is to promote small lifestyle changes to prevent the gradual increase in the body weight of populations. America On the Move is an initiative based on promoting small lifestyle changes to prevent weight gain in the US population. This is one strategy could be used in other countries to reduce obesity rates.

The role of public policy in treating the epidemic of global obesity

Given the powerful forces promoting population weight gain, the obesity epidemic cannot be reversed solely by promoting individual behavior change. Policy initiatives might lessen the impact of the biological and economical forces promoting weight gain or provide motivation to resist these forces. Unfortunately, there is little information to adequately evaluate the many policies that have been suggested. The intent of this review is to discuss the potential use of policy to stem the global epidemic of obesity.

From instinct to intellect: the challenge of maintaining healthy weight in the modern world

The global obesity epidemic is being driven in large part by a mismatch between our environment and our metabolism. Human physiology developed to function within an environment where high levels of physical activity were needed in daily life and food was inconsistently available. For most of mankind's history, physical activity has 'pulled' appetite so that the primary challenge to the physiological system for body weight control was to obtain sufficient energy intake to prevent negative energy balance and body energy loss. The current environment is characterized by a situation whereby minimal physical activity is required for daily life and food is abundant, inexpensive, high in energy density and widely available. Within this environment, food intake 'pushes' the system, and the challenge to the control system becomes to increase physical activity sufficiently to prevent positive energy balance. There does not appear to be a strong drive to increase physical activity in response to excess energy intake and there appears to be only a weak adaptive increase in resting energy expenditure in response to excess energy intake. In the modern world, the prevailing environment constitutes a constant background pressure that promotes weight gain. We propose that the modern environment has taken body weight control from an instinctual (unconscious) process to one that requires substantial cognitive effort. In the current environment, people who are not devoting substantial conscious effort to managing body weight are probably gaining weight. It is unlikely that we would be able to build the political will to undo our modern lifestyle, to change the environment back to one in which body weight control again becomes instinctual. In order to combat the growing epidemic we should focus our efforts on providing the knowledge, cognitive skills and incentives for controlling body weight and at the same time begin creating a supportive environment to allow better management of body weight.

The role of pepsin in acid injury to esophageal epithelium

OBJECTIVES

The development of reflux esophagitis in humans is a process resulting from esophageal exposure to refluxed gastric contents. There is no doubt that damage to the esophageal epithelium requires exposure to gastric acid; however, the role of refluxed pepsin as contributor to this damage seems to be underappreciated.

METHODS

The role of physiological concentrations of pepsin was examined in Ussing chambered rabbit esophageal epithelium and in cultured esophageal epithelial cells.

RESULTS

The results of this investigation reaffirmed the ability of pepsin to increase the rate and degree of esophageal cell and tissue damage at acidic pH, although the range of activity was limited to pH < 3.0. Moreover, the increased rate of tissue damage by acidified pepsin rapidly (within 15 min) produced a lesion that was irreversible, whereas, in a similar time frame, acid alone produced a lesion that was completely reversible. This early lesion by acidified pepsin was localized by performance of mannitol fluxes in apparently undamaged esophageal epithelium on light microscopy to the intercellular junctional complex. Further acid produced similar degrees of cell killing as acidified pepsin at pH < 3.0 in rabbit esophageal epithelial cells in suspension but not when growing on coverslips or present within intact epithelium.

CONCLUSIONS

These studies suggest that acidified pepsin plays a key role in the development of reflux esophagitis by producing an early irreversible lesion that results in an increase in paracellular permeability, which indirect evidence suggests is due to damage to the junctional complex. The irreversibility of the increase in paracellular permeability is likely to aid conversion of nonerosive to erosive damage to the epithelium by permitting luminal acid greater access to the basolateral membrane of esophageal epithelial cells, which is known to be acid permeable.

Genetic and environmental contributions to obesity

Groups that are already concerned about obesity can be linked together. This can generate plans of action and may lead to small-scale interventions. At the same time, awareness needs to be raised among other potential partners, especially federal, state, and local government agencies. As a partnership is built, funding opportunities, from public and private entities, should increase. The ultimate need is a public health campaign to combat an important public health problem.

Resting energy expenditure in reduced-obese subjects in the National Weight Control Registry

BACKGROUND

Weight loss in obese subjects is associated with a reduction in resting metabolic rate (RMR). Whether the reduction can be explained solely by a reduction in lean body mass remains controversial.

OBJECTIVE

Our objective was to determine whether the reduction in RMR after weight loss was proportional to the decrease in lean mass alone or was greater than could be explained by body composition.

DESIGN

We measured the RMR, fasting respiratory quotient (RQ), and body composition in 40 reduced-obese subjects [ie, 7 men and 33 women who had lost > or = 13.6 kg (30 lb) and maintained the loss for > or = 1 y] enrolled in the National Weight Control Registry and 46 weight-matched control subjects (9 men, 37 women).

RESULTS

A stepwise multiple regression found lean mass, fat mass, age, and sex to be the best predictors of RMR in both groups. After adjusting RMR for these variables, we found no significant difference in RMR (5926 +/- 106 and 6015 +/- 104 kJ/d) between the 2 groups (P = 0.35). When we adjusted fasting RQ for percentage body fat and age, the reduced-obese group had a slightly higher (0.807 +/- 0.006) RQ than the control group (0.791 +/- 0.005, P = 0.05). This may have been due to the consumption of a diet lower in fat or to a reduced capacity for fat oxidation in the reduced-obese group.

CONCLUSION

These results show that in at least some reduced-obese individuals there does not seem to be a permanent obligatory reduction in RMR beyond the expected reduction for a reduced lean mass.