This article was originally written by the Sequence clinic team (now known as WeightWatchers Clinic).

Why is it so hard to maintain weight loss? An evidence-based review

Published September 22, 2023

The prevalence of overweight and obesity has increased significantly over the past three decades and it is now estimated that 1 in 3 Americans have obesity. Of those, an estimated 50-70% are actively trying to lose weight mainly through diet and lifestyle modifications. While many individuals successfully achieve weight loss using these interventions, the bigger challenge is often sustaining that loss.

A 2013 review article discusses the physiological and psychological factors that promote weight regain and that make maintaining long-term weight loss challenging. Some key factors include changes in metabolism, hormonal regulation, increased appetite, reduced energy expenditure, and behavioral factors like overeating and reduced physical activity. To put it simply, weight management isn’t simple—it’s complex. That’s why a comprehensive approach that addresses the biological factors that drive weight regain is essential for sustainable weight loss maintenance.

Metabolic adaptation

One of the primary physiological factors is the body's adaptation to weight loss. When a person loses weight, their resting energy expenditure—the energy needed to fuel minimal daily functions like breathing, maintaining blood pressure, and digesting nutrients—decreases, making it easier for individuals regain weight when they return to a regular diet. This phenomenon is often referred to as “adaptive thermogenesis” aka “metabolic adaptation,” and it can be a significant contributor to weight regain.

Hormonal regulation

Weight loss can disrupt the hormonal balance in the body, particularly hormones that stimulate appetite like ghrelin and hormones that signal fullness like glucagon-like peptide 1 (GLP-1) and leptin. After weight loss, ghrelin levels may increase, leading to heightened hunger, while leptin and GLP-1 levels decrease, making it more challenging to feel full. This hormonal imbalance can drive overeating and contribute to weight regain in an effort to restore weight balance. These changes may relate to the body’s survival mechanisms to protect our energy stores (which may have served our species during times of famine but is the source of present-day frustrations for many). Research suggests there may also be changes to thyroid hormones and cortisol levels that can impact energy expenditure and hunger and satiety hormones.

Alterations in gastrointestinal motility

When we eat a meal, the stomach stretches to allow space for food to be digested. This abdominal distention provides feedback to the brain to signal that the stomach is full and to stop eating. Some research suggests that individuals living with obesity may have an accelerated rate of gastric emptying—meaning that food moves more quickly through their gastrointestinal tract. This may decrease the signaling from the stomach to the brain and allow increased food consumption and more frequent meals as a result.

Behavioral factors

After a period of restriction during weight loss, individuals may experience an increased desire to indulge in high-calorie, palatable foods. After all, the more we tell ourselves something is off limits, the more we want it. Restriction can lead an individual to overeat once they achieve their goal weight and undermine their weight maintenance efforts as a result. This is why it’s critical to approach weight loss without extreme restriction and focus on a nutrition plan that is sustainable and allows for some flexibility. Starting your weight loss journey with maintenance in mind can help create meaningful mental shifts that not only make the process of weight loss more enjoyable, but that make the transition from weight loss to weight maintenance much less daunting.

Special considerations for weight maintenance for individuals on a GLP-1 medication

GLP-1 medications work by mimicking the hormone GLP-1 which targets the areas of the brain that regulate appetite and food intake. Additionally, GLP-1’s slow the rate of gastric emptying which allows individuals to feel fuller for longer and control their portion sizes as a result.

Individuals on a GLP-1 medication have a unique challenge of ensuring that they are eating enough due to the appetite suppression that the medication provides. Throughout the weight loss process, it’s important to check in with frequently to determine if your rate of weight loss is appropriate, if your dietary patterns are sustainable long-term, and to ensure you are not over-restricting as severe restriction (in terms of calories and food groups) can drive weight regain due to the metabolic and hormonal impact discussed above. All of these factors underscore the importance of working with a comprehensive team who specializes in medical weight management and can provide individualized care.

In summary, the article sheds light on the complexity of weight management and the numerous interrelated factors that can make it difficult to sustain weight loss over time. It emphasizes the need for a holistic approach to weight maintenance, incorporating strategies that address both physiological and psychological aspects. Such approaches may include gradual weight loss to minimize metabolic adaptation, ongoing hormonal monitoring and support, and behavioral interventions to promote healthier eating habits and increased physical activity.