The pursuit of weight loss is a common goal, fueled by societal pressures and the desire for improved health. Americans spend over 30 billion dollars on diet products every year. It is a hugely profitable industry. And yet, to date, no diets have proven to provide long-lasting results. However, the long-term effects of prolonged dieting, often referred to as chronic dieting, can have significant and far-reaching consequences on both physical and mental well-being. Chronic dieting involves constantly cycling through various diet plans or adhering to rigid food rules in pursuit of weight loss. Whether it's following popular diets like Keto or Paleo or imposing arbitrary restrictions on specific foods or food groups, chronic dieters often find themselves trapped in a cycle of restriction, deprivation, and eventual rebound. This article delves into the multifaceted effects of prolonged dieting, exploring its impact on metabolism, hormonal balance, mental health, and social life.
Metabolic Adaptation: When Your Body Fights Back
When people lose weight, their energy needs drop more steeply than expected, due to a phenomenon called metabolic adaptation. This well-known yet little-studied effect is often blamed for long-term weight regain, but UAB researchers have found no evidence to support that. A key aspect of understanding the effects of prolonged dieting lies in the concept of metabolic adaptation.
Imagine a person who is 220 pounds and has energy needs of 2,500 calories per day,” said Cátia Martins, Ph.D., associate professor in the Department of Nutrition Sciences in the UAB School of Health Professions. “They decide to lose weight and manage to lose 22 pounds, so now they are 198 pounds. You would expect that the person needs less energy, maybe that their energy needs went to 2,200 calories. But when we measure this in a metabolic chamber for 24 hours, we find that the person needs only 2,000 calories. This exaggerated reduction in energy expenditure after weight loss is called metabolic adaptation (or, to be more specific, adaptive thermogenesis; but we’ll go with the first term).
Of all the mysteries in nutrition science, of which there are many, this may be one of the most hotly debated. When you go on a diet to lose weight, does your body fight back? It’s an intriguing idea, and one that could explain the depressing statistics around weight loss. In a 2001 meta-analysis of 29 studies of long-term weight loss, more than half of the lost weight was regained within two years, and by five years that number was 80 percent.
Cátia Martins, Ph.D., associate professor in the Department of Nutrition Sciences, has been teasing apart the mysteries of metabolic adaptation for the past 10 years, first in Norway and, since 2020, at UAB, often working closely with UAB colleagues Barbara Gower, Ph.D., and Gary Hunter, Ph.D.“There is this idea everywhere from patients to clinicians, to researchers that the main reason people regain weight after weight loss is because the body fights back,” Martins said. “But not one study has shown a link between metabolic adaptation and weight regain.
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Martins has been teasing apart the mysteries of metabolic adaptation for the past 10 years, first at the Norwegian University of Science and Technology in Trondheim and, since 2020, at UAB, often working closely with UAB colleagues Barbara Gower, Ph.D., and Gary Hunter, Ph.D. This is not to say that metabolic adaptation has no role in the struggle for weight loss. In a 2022 paper in the journal Obesity, “we found that individuals with a greater magnitude of metabolic adaptation during weight loss are those who require more time to reach their weight-loss goals and lose less weight and fat mass in response to a low-energy diet,” Martins said.
It is important to understand exactly what is happening in metabolic adaptation, including why findings in the field tend to bounce around, Martins notes. “In all of the studies, half don’t show metabolic adaptation and half do,” she said. Some show a large effect. Others, to quote the title of one of Martins’ papers in 2020, find that “metabolic adaptation is an illusion” caused by how different studies measure body composition and energy expenditure. The methodologies of studies also contribute to the illusion, Martins says. Most studies use a two-compartment model to measure weight loss: fat-free mass (water, bones, muscle, internal organs, etc.) and fat mass (fat). Other studies add a third compartment, using DXA scans to tease out bone mineral content from the other fat-free mass components. “But that still leaves muscle, organs and water,” Martins said.
Detailed studies show that is not the case, Martins noted: “Some people lose more organ and less muscle. Weight loss is followed by a reduction in several organ sizes, including the heart, pancreas and kidneys.” (This paper led by researchers in New York, reports that, in participants who lost 11 percent of body weight, heart mass decreased by 26 percent and the kidneys by 19 percent.) And it is important to note that the metabolic rate of organs is much higher than that of muscles, Martins says. “For some organs, it is up to 20 times higher. The problem is we do not have any studies looking at metabolic adaptation at the level of total energy expenditure with prediction models looking at the different components of fat-free mass.
The new study proposed by Martins and Fernando Bril, M.D., will test a diet intervention based on the appetite-suppressant effects of a low-carb ketogenic diet in patients who have lost at least 10 percent of body weight on semaglutide (Ozempic) or other GLP-1 agonist drugs. The chief mechanisms of action of these drugs "seem to be reducing appetite and food intake,” Martins said. This is exactly what Martins has proposed in a pending grant application to the NIH. “I want to quantify all of these things: total energy expenditure measured in a metabolic chamber and body composition using MRI and DXA, to come up with prediction models based on changes in fat, muscle and organ mass,” she said. Ideally, weight loss would be targeted as much as possible to fat loss - and to addressing the hunger that makes diets so difficult to stick with.
Martins has another proposal under consideration for a clinical trial studying this in patients who have used new GLP-1 agonist drugs such as Ozempic to lose weight but stopped using them. The drugs are expensive and in short supply, however, and the effects of long-term - potentially lifelong - use of GLP-1 agonists is unknown. “When individuals stop taking these drugs, they experience weight regain of up to two-thirds of the initial weight loss one year after stopping,” Martins said.
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Martins’ preliminary research on low-carb ketogenic diets shows that they do not trigger the upregulation of the hunger hormone ghrelin that is normally seen when dieting. “As long as the person is ketotic, ghrelin and subjective hunger feelings do not increase,” Martins said. The new study proposed by Martins and Fernando Bril, M.D., assistant professor in the Department of Medicine’s Division of Endocrinology, Diabetes and Metabolism, will test a diet intervention based on the appetite-suppressant effects of a low-carb ketogenic diet. “The main mechanisms of action of these GLP-1 agonist drugs seem to be reducing appetite and food intake, even though energy expenditure might also be involved,” Martins said.
Martins’ preliminary research on low-carb ketogenic diets shows that they do not trigger the upregulation of the hunger hormone ghrelin that is normally seen when dieting. “As long as the person is ketotic, ghrelin and subjective hunger feelings do not increase,” Martins said. “We plan to put participants through a two-week weight maintenance diet and then randomize them to a low-carb ketogenic diet or standard care (a low-fat diet) for 12 weeks, with all food provided,” Martins said. “This will be followed by a six months follow-up with dietary prescription to look at the feasibility of these diets in real life. Our hypothesis is the participants on the low-carb ketogenic diet will not increase food intake, while it will be the opposite with the participants on the low-fat diet. Evidence does show that low-carb ketogenic diets buffer appetite and increase energy expenditure, which could favor weight-loss maintenance. We will see.”
Aggressive dieting lowers the base metabolic rate, meaning one burns less energy when resting, resulting in significantly lower daily needs in order to sustain achieved weight after the diet is over. Returning to normalized eating habits at this lower base metabolic rate results in commonly seen post dieting weight gain.
Recent data examining 14 participants in the “Biggest Loser” contest showed they lost on average 128 pounds and their baseline resting metabolic rates dropped from 2,607 +/-649 kilocalories/ day to 1,996 +/- 358 kcal/day at the end of the 30 weeks contest. Those that lost the most weight saw the biggest drops in their metabolic rate. Proportional to their individual weights the contestants were burning a mean of ~500 fewer kilocalories a day than would be expected of people their sizes, leading to steady weight gain over the years.
The Downside of Chronic Dieting
Chronic dieting takes a toll on the body beyond just the numbers on the scale. While the short-term effects may seem manageable, the long-term consequences of restrictive eating habits can be significant and far-reaching. In this section, we'll explore how chronic dieting can lead to nutritional deficiencies, metabolic changes, and hormonal imbalances, undermining overall health and well-being.
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Nutritional Deficiencies
One of the most significant risks associated with chronic dieting is the potential for nutrient deficiencies. By restricting food intake or eliminating entire food groups, chronic dieters may fail to meet their body's essential nutrient needs, leading to deficiencies in vitamins, minerals, and other vital nutrients. Common deficiencies associated with chronic dieting include:
- Inadequate intake of micronutrients such as iron, calcium, vitamin D, and B vitamins.
- Insufficient dietary fiber, leading to digestive issues and impaired gut health.
- Low levels of essential fatty acids, which are crucial for brain function and hormone production.
Metabolic Changes
Chronic dieting can also have profound effects on metabolic function, disrupting the body's natural energy balance and regulatory mechanisms. When faced with prolonged periods of calorie restriction, the body responds by slowing down metabolism and conserving energy in an effort to preserve vital functions. This metabolic adaptation can lead to:
- Reduced resting metabolic rate, making it harder to lose weight and maintain weight loss.
- Increased propensity for weight regain following periods of dietary restriction.
- Altered levels of hunger hormones, such as leptin and ghrelin, contributing to increased appetite and cravings.
- Worsened metabolic markers such as insulin resistance and lipids
Hormonal Imbalances
Hormonal dysregulation is another common consequence of chronic dieting, impacting various systems throughout the body. The human body often relies on a delicate balance of hormones to regulate metabolism, mood, energy levels, and reproductive function. Chronic dieting, especially when aimed at weight loss, can disrupt this balance, leading to significant effects on body weight and overall health. This imbalance can manifest in several ways, affecting not just your weight loss efforts but also leading to broader systemic issues.
Mental Health Implications
Chronic dieting takes a significant toll on mental health, manifesting in various psychological challenges. In this section, we'll explore how chronic dieting contributes to such health problems: body dysmorphia, eating disorders, anxiety, and depression.
Body Dysmorphia
Chronic dieting often leads to body dysmorphia. This condition involves a distorted perception of one's body size, shape, or appearance, leading to obsessive thoughts and behaviors related to body image. Chronic dieters often fixate on perceived flaws or imperfections, regardless of their actual physical appearance. The relentless pursuit of an idealized body shape or size can lead to dissatisfaction, low self-esteem, and negative body image.
Eating Disorders
Chronic dieting can escalate into eating disorders. In fact, around 20-25% of diets result in ED’s, such as anorexia nervosa, bulimia nervosa, or binge eating disorder. Restrictive eating patterns and rigid food rules perpetuate cycles of guilt and shame, eroding self-worth.
Diets imply restriction. Psychologically, dietary restraint can lead to greater reactivity to food cues, increased cravings and disinhibition, and overeating and binge eating. Dieting emphasizes food as “good” or “bad”, as a reward or punishment, and increases food obsessions. It does not teach healthy eating habits and rarely focuses on the nutritional value of foods and the benefit of regulated eating. Unsatisfied hunger increases mood swings and risk of overeating. Restricting food, despite drinking enough fluids, can lead to dehydration and further complications, like constipation.
Anxiety and Depression
The psychological toll of chronic dieting extends beyond body image concerns and eating behaviors, impacting overall mental well-being. Research has shown a strong correlation between chronic dieting and increased risks of anxiety and depression. The pressure to adhere to strict dietary rules and fear of weight gain contribute to increased anxiety and depression among chronic dieters. The constant cycle of success and failure in dieting exacerbates feelings of hopelessness and despair.
Social Implications of Chronic Dieting
Chronic dieting doesn't just affect individuals internally; it also has profound implications for their social lives and relationships. The relentless focus on food and weight inherent in chronic dieting strains personal relationships, leads to social isolation, and disrupts social interactions. Fear of deviating from the diet plan and discomfort in social settings where food is present can cause chronic dieters to withdraw from social activities, creating tension and misunderstanding with friends, family members, and romantic partners.
Breaking Free: A Path Towards a Healthier Relationship with Food
Breaking free from the cycle of chronic dieting requires a shift in mindset and behavior. Below are some strategies for recognizing harmful patterns, seeking support, and building a healthy relationship with food and body.
Recognizing Harmful Patterns
Identifying unhealthy dieting behaviors is the first step toward breaking the cycle of chronic dieting. Some tips for recognizing harmful patterns include:
- Becoming aware of rigid food rules and restrictions that contribute to feelings of guilt and shame. Having rigidity around food rules and becoming very stressed or anxious if you cannot follow said rules. Rigidity around food rules and heightened stress or anxiety when unable to adhere to them.
- Monitoring thoughts and behaviors related to food, weight, and body image, and challenging negative self-talk.
- Paying attention to physical and emotional cues, such as hunger and fullness signals, rather than relying on external rules or cues.
Seeking Support
Professional guidance from dietitians, therapists, and support groups can be invaluable in overcoming chronic dieting. Seeking support from qualified professionals can help individuals:
- Explore underlying factors contributing to chronic dieting behaviors, such as past trauma, societal pressures, or low self-esteem.
- Develop personalized strategies for establishing a balanced approach to eating and cultivating a positive body image.
- Receive emotional support and encouragement from peers who understand the challenges of overcoming chronic dieting.
Building a Healthy Relationship with Food and Body
Fostering a healthy relationship with food and body is essential for long-term well-being. Some strategies for building a positive relationship include:
- Practicing intuitive eating, which involves listening to the body's hunger and fullness cues and honoring its nutritional needs without judgment.
- Cultivating self-compassion and acceptance by reframing negative thoughts and beliefs about food, weight, and body image.
- Engaging in enjoyable physical activities that promote health and vitality, rather than focusing solely on exercise as a means of weight control. Exercise may not be very effective for weight loss, but fitness is more important to health and longevity than weight is, so exercise is worth prioritizing.
Fad Diets: A Quick Fix with Long-Term Consequences
Fad diets have grown in popularity in recent years, fueled by social media use and society’s pressure to be thin. These diets promise quick weight loss and health changes but can harm your health due to unrealistic claims. So, what are fad diets? A fad diet is a diet that becomes very popular. Some promote high intake of a certain food, like grapefruit or celery juice. Others will focus on eliminating certain foods overall. Popular fad diets often lead to rapid, short-term weight loss.
Fad diets can be harmful to your health and are often not safe in the long term. If a diet sounds too good to be true, or if it cuts out entire food groups, it is probably not a manageable lifestyle.
Sustainable Alternatives for a Healthier Lifestyle
It's essential to recognize the differences between chronic dieting and sustainable healthy habits. To me, it is of utmost importance that people understand there are other ways to be healthy outside of restrictive diets. And ultimately, the methods I recommend are much healthier, as we know weight cycling (going up and down in weight) is bad for our health and can lead to a disordered relationship with food.
Consulting a Registered Dietitian
The best approach is to consult a Registered Dietitian, the trusted food and nutrition expert. They can provide tailored advice based on scientific evidence from reputable organizations and government health agencies.
Gradual and Sustainable Changes
Aim for gradual and sustainable changes. Losing one to two pounds per week is a healthy approach. Making small, manageable changes to your current eating habits may be the most doable option.
Balanced Nutrition
Focus on balanced nutrition, including a variety of foods from all food groups (fruits, vegetables, grains, dairy, and protein foods). Another good place for healthy nutrition advice is ChooseMyPlate.gov.