Various dietary approaches with different caloric content and macronutrient composition have been recommended to treat obesity in adults. As a general principle, the optimal diet to treat obesity should be safe, efficacious, healthy and nutritionally adequate, culturally acceptable and economically affordable, and should ensure long-term compliance and maintenance of weight loss. Setting realistic goals for weight loss and pursuing a balanced dietary plan tailored to individual needs, preferences, and medical conditions, are the key principles to facilitate weight loss in obese patients and most importantly reduce their overall cardiometabolic risk and other obesity-related comorbidities.
Various dietary guidelines for weight loss
Identifying safe and effective strategies for long-term weight control is critical to reduce the alarming prevalence of overweight and obesity in adults and adolescents worldwide and mitigate obesity-associated health risks. Obesity and overweight affect together over a third of the world’s
population today, and if current trends continue, an estimated 38% of the world’s adult population will be overweight and another 20% will be obese by 2030. Although obesity is a complex and multifactorial disease with genetic, behavioral, socioeconomic, and environmental origins, it is also preventable and treatable to a great extent. There is no doubt that the first-line treatment of obesity is dietary management combined with behavior modification, and secondarily, increased physical activity. Weight loss medication and bariatric surgery are further recommended for specific subgroups of obese patients.
Dietary guidelines for weight loss vary greatly between different scientific societies and have been revised many times, reflecting the uncertainty in the field of nutritional management of obesity and the difficulty to generate uniform recommendations for all patients. There are dozens of weight loss diets promising to reduce body weight. However, the key to successful weight loss lies in the prudent combination of all these approaches in the context of a healthy and balanced diet without severe restrictions or nutritional exaggerations. This article aims to provide to define the optimal dietary approach for a safe, effective, and sustainable weight loss in overweight and obese adults.
Low- fat diets
Low-fat diets have been recommended as safe and effective weight loss strategies for many decades on the basis of several observations: (1) energy from fat is less satiating than energy from carbohydrate, and a high fat/carbohydrate ratio in the diet can promote passive overconsumption, positive energy balance and weight gain in susceptible individuals; (2) fat is more readily absorbed from the intestine than carbohydrate and fecal energy loss is much lower with a high dietary fat/carbohydrate ratio; (3) carbohydrate is more thermogenic than fat and energy expenditure is lower during a diet with a high fat/carbohydrate ratio than during a diet with a low fat/carbohydrate ratio; and (4) a high-fat diet may damage the intestinal barrier and cause intestinal dysbiosis with an adverse impact on body weight and metabolic variables.
Another reason for lowering the proportion of calories consumed from fat is that a single gram of fat contains more than twice the calories of a gram of carbohydrates or protein (9 kcal/gram vs. 4 kcal/gram). Thus, reducing total fat intake may theoretically lead to a considerable effect on total amount of calories consumed. Despite the above theoretical considerations, randomized trials have failed to consistently demonstrate that reducing fat intake may be superior to other dietary interventions in terms of long-term weight loss. In a meta-analysis comparing several popular weight loss diets, low-fat diets were found to be equally effective as other diets in terms of weight loss, without however reporting any differences between diets in qualitative aspects, compliance rates and adverse events.
Another study has shown that both low-fat and higher-fat diets have similar effects on weight loss, total and visceral fat loss, and lean body mass preservation. Both diets were characterized by low intake of saturated fat and foods of high glycemic index and an increased intake of fiber-rich foods, suggesting that when standards of a high-quality diet are met, variations in macronutrient composition play a secondary role for weight loss. In another systematic review and meta-analysis comparing low-fat diets with other dietary interventions, it was found that the long-term effect of low-fat diets on body weight depends primarily on the intensity of diet intervention in the comparison group. When compared to usual diets, low-fat diets are indeed more effective in weight reduction with a slight to modest effect. However, when compared to other higher-fat dietary interventions of similar intensity such as low-carbohydrate diets and especially when high adherence rates are achieved, low-fat diets are equally or less effective in achieving significant long-term weight control. The most effective strategy to achieve long-term weight loss and good cardiometabolic health is shifting to a healthy dietary pattern.
Karimi, H.
Master of clinical Nutrition & Dietetics
Reference
- Koliaki C. Defining the Optimal Dietary Approach for Safe, Effective and Sustainable Weight Loss in Overweight and Obese adults. Healthcare. 2018.
