Excess weight and weight gain during adult life significantly elevate the risk of several diseases, including diabetes, cardiovascular disease (CVD), dementia, and certain cancers like breast cancer, potentially leading to premature death. Modest weight reduction (more than 5% of body weight) has shown promise in reducing the incidence and progression of these diseases. However, poor compliance in weight loss programs remains a significant challenge, and even when weight loss is achieved, the benefits may diminish due to non-compliance or adaptation. Therefore, sustainable and effective energy restriction strategies are crucial.
One such approach is intermittent energy restriction (IER), which involves short periods of severe energy restriction interspersed with longer periods of habitual energy intake. IER has been extensively studied in rodent models, demonstrating its effectiveness in improving insulin sensitivity, preventing mammary tumors, delaying prostate cancer onset, increasing resistance to neuronal damage, reducing cognitive impairment, protecting the heart, and extending lifespan. In some cases, IER has shown similar benefits to more stringent continuous energy restriction (CER).
Study Design and Methods
A randomized controlled trial was conducted to compare the effectiveness of IER and CER in overweight or obese premenopausal women. The study involved 107 women aged 30 to 45 years with a body mass index (BMI) between 24 and 40 kg/m2 and a history of adult weight gain exceeding 10 kg since the age of 20. Participants were recruited from a Breast Cancer Family History Clinic and the general population, with 54% having a family history of breast cancer.
The participants were non-smokers, not currently dieting, had regular menstrual cycles, and no evidence of hyperandrogenism or polycystic ovary syndrome. They also had no oral contraceptive use during the previous 6 months and did not have high intakes of alcohol or phytoestrogens. Exclusion criteria included diagnosed diabetes, CVD, major psychiatric morbidity, or cancer.
The women were randomly assigned to either the IER group or the CER group. The CER group was prescribed a daily 25% energy restriction based on a Mediterranean-type diet (30% fat, 15% monounsaturated, 7% saturated fat, 7% polyunsaturated fatty acids, 45% low glycemic load carbohydrate, and 25% protein). The IER group followed a very low-calorie diet (VLCD) on two consecutive days per week, restricting energy intake by 75%, and consumed estimated requirements for weight maintenance for the remaining five days, adhering to the same nutrient composition as the CER group. The VLCD provided 2060 to 2266 kJ of energy and 50 g protein per day, consisting of semi-skimmed milk, vegetables, fruit, a salty low-calorie drink, and a multivitamin and mineral supplement.
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Measurements were taken at baseline, 1 month, 3 months, and 6 months, including weight, total body fat, fat-free mass (FFM), waist, hip, bust, and thigh circumference, systolic and diastolic blood pressure (BP), and blood sampling. Adherence to the dietary interventions was assessed using 7-day food diaries, and physical activity was assessed using the International Physical Activity Questionnaire (IPAQ).
Key Findings
Weight Loss and Body Composition
Last observation carried forward (LOCF) analysis at 6 months demonstrated that IER and CER were equally effective for weight loss. The mean weight change for the IER group was -6.4 kg, while the CER group experienced a mean weight change of -5.6 kg. There was no statistically significant difference between the groups. Both groups showed comparable reductions in body fat, FFM, hip, bust, and thigh circumference, as well as similar compositions of weight loss.
Metabolic and Hormonal Changes
Both groups experienced comparable reductions in leptin, free androgen index, high sensitivity C-reactive protein, total and LDL cholesterol, triglycerides, and blood pressure. Additionally, both groups showed increases in sex hormone-binding globulin, IGF binding proteins 1 and 2. These findings suggest that both IER and CER can lead to similar improvements in metabolic and hormonal profiles.
Adherence and Tolerability
Adherence to the dietary interventions was assessed using 7-day food diaries. Intention-to-treat analysis showed that 63% of the IER group reported adhering to the 2-day VLCD at 1 month, 43% at 3 months, and 44% at 6 months. The proportion of CER subjects reporting adhering to the 25% CER was 46% at 1 month, 37% at 3 months, and 32% at 6 months. At the end of the trial, 58% of IER and 85% of CER subjects planned to continue the diet allocated at randomization.
Implications and Significance
This study provides evidence that IER can be as effective as CER for weight loss and improving metabolic health in overweight or obese premenopausal women. The findings suggest that IER may be a viable alternative for individuals who find it difficult to adhere to continuous energy restriction. The comparable improvements in metabolic and hormonal profiles between the two groups indicate that IER can offer similar health benefits to CER.
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Broader Context: Weight Loss and Metabolic Health
The study's findings align with a broader understanding of weight loss and its impact on metabolic health. Observational and randomized trials have consistently shown that even modest weight loss (greater than 5% of body weight) can significantly reduce the risk and progression of various diseases. This underscores the importance of developing sustainable and effective weight loss strategies to combat the growing global prevalence of overweight and obesity.
The Role of Diet Composition
The study emphasizes the importance of diet composition in both IER and CER approaches. The Mediterranean-type diet, with its focus on healthy fats, low glycemic load carbohydrates, and adequate protein, provides a balanced and sustainable dietary framework for weight loss and metabolic health. This type of diet is known for its anti-inflammatory properties and its ability to improve insulin sensitivity and lipid profiles.
The Importance of Long-Term Adherence
While both IER and CER can be effective for weight loss, long-term adherence remains a critical factor in maintaining weight loss and sustaining the associated health benefits. The study's findings highlight the challenges of achieving high levels of adherence to both IER and CER over a 6-month period. This underscores the need for personalized weight loss strategies that consider individual preferences, lifestyles, and psychological factors to promote long-term adherence.
Future Research Directions
Future research should focus on identifying factors that predict adherence to IER and CER, as well as developing strategies to improve adherence and long-term weight loss maintenance. Additional studies are needed to explore the effects of different IER protocols, such as varying the duration and frequency of energy restriction periods. Furthermore, research should investigate the potential benefits of combining IER with other lifestyle interventions, such as exercise and behavioral therapy.
Mark's Weight Loss Journey: A Real-World Example
To illustrate the impact of weight loss on overall well-being, consider the story of Mark, a 59-year-old who successfully lost weight and improved his health through a structured weight loss program. Mark's experience highlights the transformative effects of weight loss on physical health, energy levels, and overall quality of life.
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Mark's journey began with a realization that his health problems and increasing weight were hindering his plans for an active and enjoyable retirement. He embarked on a weight loss program and experienced remarkable results, losing approximately 18 kg in a matter of months.
Mark's success can be attributed to several factors, including a sustainable dietary approach, regular exercise, and a supportive program that provided guidance and motivation. His story exemplifies the potential for individuals to achieve significant weight loss and improve their health through a combination of lifestyle changes and professional support.
The Broader Implications of Weight Management
Mark's experience underscores the broader implications of weight management for individuals and society as a whole. By addressing weight-related health issues, individuals can reduce their risk of chronic diseases, improve their quality of life, and extend their lifespan. Furthermore, effective weight management strategies can contribute to reducing healthcare costs and improving overall public health.
The Role of Sweeteners and Sweetness Enhancers (S&SEs) in Weight Management
The use of sweeteners and sweetness enhancers (S&SEs) in weight management has been a topic of ongoing debate. While S&SEs are generally considered safe, their long-term effects on cardiometabolic health and gut microbiota composition remain uncertain.
Some studies have raised concerns about potential risks associated with S&SE consumption, while others have shown neutral or beneficial effects, including modest weight loss and no negative impact on type 2 diabetes or cardiovascular disease risk markers. The conflicting evidence highlights the need for controlled, long-term studies to directly assess the impact of replacing sugar with S&SEs on metabolic outcomes.
The SWEET Project: Investigating the Effects of S&SEs on Weight Loss Maintenance
The SWEET project is a large-scale randomized controlled trial designed to assess the effect of combined and prolonged use of S&SEs on weight loss maintenance, cardiometabolic risk factors, and gut microbiota composition in adults with overweight or obesity. The study aims to determine whether the inclusion of S&SEs in foods and drinks can improve compliance with a healthy, sugar-reduced diet, resulting in better control of body weight and related risk factors.
Study Design and Methods of the SWEET project
The SWEET project included 341 adults and 38 children, who were randomly assigned to either a sugar group or an S&SEs group. The primary outcomes of the study were 1-year changes in body weight and gut microbiota composition in adults. Secondary outcomes included changes in risk factors for type 2 diabetes and cardiovascular disease, body mass index (BMI)-for-age z-score in children, intrahepatic lipid (IHL) content, adverse events, gastrointestinal symptoms, and use of concomitant medication.
Key Findings of the SWEET project
Preliminary results from the SWEET project suggest that the S&SEs group maintained a larger weight loss than the sugar group over the 1-year study period. Additionally, the study found that the S&SEs group exhibited distinct shifts in microbial communities in the gut, with increased overall abundance of multiple short-chain fatty acid (SCFA)-producing genera.
Implications and Significance of the SWEET project
The SWEET project's findings provide valuable insights into the potential role of S&SEs in weight management and metabolic health. The results suggest that S&SEs may be a useful tool for improving adherence to a healthy, sugar-reduced diet and promoting weight loss maintenance. However, further research is needed to fully understand the long-term effects of S&SEs on gut microbiota composition and overall health.
The Gut Microbiota and Weight Management
The gut microbiota, the complex community of microorganisms residing in the digestive tract, plays a crucial role in human health and metabolism. Emerging evidence suggests that the gut microbiota may influence weight management by affecting energy harvest from food, regulating appetite and satiety, and modulating systemic inflammation.
The Impact of Diet on the Gut Microbiota
Diet is a major determinant of gut microbiota composition and function. Different dietary patterns can promote the growth of different types of bacteria, leading to shifts in the overall microbial community. For example, diets high in fiber and plant-based foods tend to promote the growth of beneficial bacteria that produce SCFAs, while diets high in saturated fat and added sugar may promote the growth of bacteria associated with inflammation and metabolic dysfunction.
The Role of SCFAs in Weight Management
SCFAs, such as acetate, propionate, and butyrate, are produced by the fermentation of dietary fiber in the gut. SCFAs have been shown to have various beneficial effects on metabolic health, including improving insulin sensitivity, reducing inflammation, and promoting satiety. By increasing the abundance of SCFA-producing bacteria in the gut, dietary interventions may improve weight management and reduce the risk of metabolic diseases.