Sustained weight loss is a multifaceted challenge. While numerous diets and exercise strategies promise quick results, successful weight loss requires a comprehensive approach encompassing dietary adjustments, increased physical activity, and behavioral modifications. A common frustration arises when individuals experience a weight loss plateau, where progress halts despite continued effort. This article explores the physiological mechanisms behind weight loss plateaus and provides evidence-based strategies to help individuals overcome them.
The Frustration of the Plateau
The weight loss journey often begins with steady progress, but many individuals encounter a plateau as their bodies adapt to changes in diet and physical activity. These biological adaptations, including a decreased resting metabolic rate and hormonal changes, can hinder continued weight loss. Physiologically, these changes can reduce energy levels and endurance, decrease fat oxidation, and increase hunger. Psychologically, the sudden halt in progress can be discouraging.
Clinicians' understanding of the basis of the weight loss plateau is critical for effective patient management. Research demonstrates that while various diets produce similar weight loss over an 8- to 12-week period, maintaining weight loss long-term (greater than 24 weeks) is successful in only about 10% to 20% of individuals. Patient frustration with a weight loss plateau contributes to the phenomenon of "yo-yo dieting," as individuals lose weight, reach a plateau, and regain the lost weight. Popular misconceptions that weight loss is a linear process exacerbate this issue, often leading to unrealistic expectations and disappointment.
To help patients overcome these challenges, healthcare professionals must identify the causes of weight loss plateaus and implement practical strategies, such as varying caloric intake, adjusting exercise routines, and incorporating behavioral techniques supported by setting reasonable expectations and motivational counseling.
The Prevalence of Obesity and the Importance of Intervention
More than 35% of men and 40% of women in the United States have obesity. The United States Preventive Services Task Force (USPSTF) guidelines, most recently updated in 2018, recommend universal obesity screening in primary care and intensive lifestyle interventions for individuals with obesity. The American Association of Clinical Endocrinologists guidelines also promote a structured lifestyle approach that includes healthy eating, exercise, and behavior modification for all individuals with overweight or obesity. In addition to recommending a comprehensive weight management program based on dietary changes, physical activity, and behavioral interventions, the National Institute for Health and Care (NICE) outlines the role of pharmacotherapy and bariatric surgery for those with inadequate weight loss after lifestyle modifications.
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Weight loss plateaus, characterized by weight loss slowing or stopping despite an individual continuing a diet and exercise regimen, affect approximately 85% of dieters. From an evolutionary perspective, stored fat is a protective reserve against periods of food scarcity, and the body resists attempts at significant weight reduction. Weight loss plateaus are complex and determined by physiologic, genetic, environmental, and psychological factors. The body adapts to reduced caloric intake with metabolic adaptations. External influences like the food environment and behavioral fatigue resulting in increased food intake and decreased physical activity contribute to the tendency for weight loss to halt and for people to regain lost pounds slowly over time.
Regardless of the type of diet, plateaus occur weeks to months following the initiation of a weight management program. The American College of Cardiology (ACC) and the American Heart Association (AHA) indicate individuals generally achieve maximal weight loss at 6 months, followed by weight maintenance or slow regain. According to the American Association of Clinical Endocrinologists and the American College of Endocrinology guidelines, weight loss plateaus with pharmacologic treatment typically occur later than with lifestyle intervention, between 6 and 12 months.
Understanding the mechanisms behind these plateaus, including hormonal regulation, metabolic adaptations, and theoretical models of weight regulation, is crucial when counseling about weight loss strategies. Clinicians who educate patients about the body's natural adaptations to weight loss and proactively address these challenges can support individuals confronting weight loss plateaus.
The Caloric Deficit: The Foundation of Weight Loss
Individuals lose weight when they achieve a calorie deficit, defined as calories consumed less than calories expended. Popular regimens, such as low-carbohydrate, ketogenic, low-fat, DASH, and Mediterranean diets, offer different macronutrient compositions but share the goal of establishing a caloric deficit to facilitate weight loss. Increasing physical activity as a sole weight loss method or in conjunction with diet can also induce a caloric deficit. The best diet is one that the individual can consistently follow while maintaining a negative energy balance.
Calculating the total daily energy expenditure (TDEE) is crucial to weight loss planning. The basal metabolic rate (BMR) or resting energy expenditure (REE), often used interchangeably, primarily determines TDEE. Non-resting energy expenditure (NREE), subdivided into exercise activity thermogenesis (EAT), non-exercise activity thermogenesis (NEAT), and the thermic effect of food, comprises the remainder of TDEE. To determine TDEE, clinicians first estimate the BMR using formulas like the Harris-Benedict or Mifflin-St Jeor equations, using body weight, height, gender, and age. Multiplying the calculated BMR by an activity factor reflecting the individual's level of physical activity (ranging from 1.2 for sedentary to 1.9 for very active) estimates the TDEE. For example, a moderately active 30-year-old woman with a weight of 70 kg and a height of 165 cm has a BMR of approximately 1400 calories daily. The BMR is multiplied by 1.6 (for moderate activity), giving an estimated TDEE of 2240 calories, the number of calories required to maintain her current weight.
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An energy deficit of 500 to 750 kcal per day usually results in a weight loss of approximately 1 to 2 lb (0.5 to 1 kg) per week, according to ACC, AHA, and The Obesity Society guidelines. Aiming for a weekly weight loss of approximately 0.7% of body weight maximizes fat loss while minimizing metabolic adaptations and muscle loss.
Physiological Adaptations: The Body Fights Back
Adaptive thermogenesis is the primary physiological adaptation that contributes to weight loss plateaus, slowing or halting weight loss as the body's REE decreases to match the lower caloric intake. REE reduction is greater than the extent predicted by the loss of fat-free mass alone. A lower BMR or REE leads to a lower TDEE. The decrease in BMR may reduce mitochondrial uncoupling protein activity, decrease thermogenesis, and reduce cellular heat production. Consequently, the body becomes more efficient at conserving energy, further contributing to the plateau.
Calorie restriction and weight loss also disrupt energy homeostasis, increasing hunger and maintaining fat stores. These adaptations can decrease leptin levels, increase ghrelin levels, and reduce overall energy expenditure, making it more difficult to lose weight. Weight loss causes loss of adipose tissue and lean mass, and the resulting smaller body mass burns fewer calories during NEAT, further contributing to the plateau. These changes increase hunger and fatigue, often leading to discouragement and diet cessation with resultant weight gain.
Hormonal Influences on Weight Loss
Several hormones are critical in regulating energy expenditure and hunger during weight loss. Leptin, produced by adipocytes, promotes satiety and increases energy expenditure. It circulates roughly in proportion to fat stores, signaling to the brain about the body's level of adiposity compared to baseline. Leptin levels decrease during weight loss due to reduced fat mass, while pre-existing leptin receptor resistance developed in response to longtime, obesity-associated elevated leptin levels may persist. These promote more food consumption and less energy expenditure.
Ghrelin, known as the "hunger hormone," stimulates appetite, triiodothyronine (T3) influences the metabolic rate, and insulin regulates macronutrient metabolism and inhibits muscle protein breakdown. Other vital hormones include pro-opiomelanocortin and glucagon-like peptide-1 (GLP-1), which regulate appetite and energy expenditure. A reduction in GLP-1 levels can lead to increased appetite. Peptide YY (PYY), released by the ileum and colon in response to food intake, acts on Y2 brain receptors to promote satiety and reduce food intake. However, PYY levels can decrease during weight loss, reducing the feeling of fullness. Neuropeptide Y, a potent appetite-stimulating neurotransmitter, increases during caloric restriction, promoting food intake, decreasing energy expenditure, and counteracting weight loss efforts.
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Theoretical Models of Weight Regulation
No one theoretical model of the complex interactions between genes and the environment in regulating body weight and adiposity thoroughly explains the observations from scientific studies. The set point theory and the settling point theory are the best-known theories. More research is needed to fully understand the physiologic basis of weight loss plateaus.
Set Point Theory
The set point theory proposes that a predetermined or "set" level maintained by physiological mechanisms regulates body weight. An active feedback system in the hypothalamus monitors and adjusts energy intake and expenditure to maintain body weight around a genetically predetermined set point. Evidence supporting this theory includes the body's resistance to weight changes through altered metabolism and appetite regulation mechanisms. However, the set point theory does not account for environmental and social influences on obesity or the widespread increase in obesity rates since the 1980s. It also does not explain why many people gain weight over holidays and weekends with wide fluctuations of weight over a year. Although the average weight of a population is relatively stable, much variability exists at the individual level. In general, humans' overall regulation of body weight is not very good, and the fact that many people overeat at certain times of the year suggests a weak level of physiologic control over energy intake. More substantial evidence from animal trials supports the existence of a body fatness or adiposity set-point rather than a weight set-point. In studies of calorie restriction leading to decreased fat stores, a period of hyperphagia and hypometabolism follows, likely involving leptin signaling the brain about the levels of adipose stores.
Settling Point Theory
In contrast, the settling point, or control theory, proposes that body weight is not actively regulated around a set point but rather "settles" or stabilizes at a point where energy intake and expenditure are balanced, influenced by factors such as diet, physical activity, genetic predisposition, and external influences. This model suggests that body weight results from passive feedback mechanisms, with changes in body adipose stores influencing energy intake and expenditure. The settling point theory accommodates the impact of social and environmental factors on body weight and better explains the obesity epidemic of recent decades. However, it does not fully address biological and genetic aspects of weight regulation.
Dynamic Equilibrium Model
Another theory, the dynamic equilibrium model, hypothesizes that a balance between energy intake and expenditure regulates body weight while acknowledging this balance is adaptable and responsive to various internal and external influences. Unlike the set-point model, this theory considers body weight as a flexible range rather than a single target. It helps explain why people hit plateaus during weight loss as the body adapts to defend its prior state, adjusting hunger and metabolic rate to favor weight regain when caloric intake is increased. In the dynamic equilibrium model, changes in body weight in either direction cause involuntary changes in energy expenditure, and people usually find a balance that can move in either direction over time. Other theoretical models are the Hall-Guo set point, the Operating Point, and the Dual Intervervention Point models.
Strategies to Overcome Weight Loss Plateaus
As a first step in managing weight loss plateaus, clinicians should provide anticipatory guidance about the physiologic changes and their effects on weight loss. Patients who understand the mechanism will more likely embrace effective strategies for achieving sustainable calorie deficits by adjusting their diet and physical activity.
Clinicians should reassess each patient with an updated dietary intake and exercise history, noting any changes in eating habits or activity levels. Ongoing weight loss stimulates appetite by activating the feedback control circuit, and consuming fewer calories requires more effort. Even intermittent lack of adherence to dietary prescriptions can cause weight fluctuations and a plateau. Patients might not be aware that they have gradually begun eating more than they did previously. Sometimes, the plateau reflects that the individual has reached an optimal BMI, and clinicians can commend and advise them on maintaining their new weight.
Several strategies exist for individuals who continue to have an elevated BMI to overcome a weight loss plateau. Patients who experience fatigue and have lost a lot of lean mass may need a "recovery phase" to regain lost muscle and positively impact their metabolism. Additional calories can decrease hunger, improve energy, and normalize altered hormonal levels during a short-term recovery period. Helpful dietary changes include a protein intake of 1.2 to 1.5 g/kg/day to preserve lean mass and promote satiety. In one small European study, consuming a diet with 25% of calories from protein led to a negative energy balance and a higher REE. Eating more fiber-rich foods will lessen hunger by delivering fewer calories per volume of food and slowing gastric emptying time.
Here are additional tips that can help you drop belly fat and break through weight loss plateaus:
- Watch your calorie intake: Maintaining a calorie deficit is essential for weight loss, including belly fat. Keep track of your calorie intake and aim to consume fewer calories than you burn.
- Exercise regularly: Incorporating both cardiovascular exercise and strength training into your fitness routine can help you lose belly fat. Cardiovascular exercise can help burn calories and fat, while strength training can help build lean muscle and boost metabolism.
- Eat a healthy diet: Focus on consuming a diet that is rich in fiber, lean protein, and healthy fats, and limit your intake of processed and sugary foods.
- Reduce stress: Chronic stress can lead to an increase in cortisol, a stress hormone, which can cause weight gain, particularly in the belly area. Find healthy ways to manage stress, such as exercise, meditation, or spending time with loved ones.