Yes, several eating disorders can cause weight gain, and even those typically associated with weight loss can lead to weight gain through biological mechanisms that disrupt metabolism and hunger signaling. The relationship between eating disorders and weight is more complex than most people realize. Binge eating disorder is the most direct driver of weight gain, but bulimia, restrictive eating patterns, and other disordered eating behaviors can all shift weight upward over time.
Binge Eating Disorder and Weight Gain
Binge eating disorder (BED) is the eating disorder most strongly linked to weight gain. It affects roughly 3.5% of adult women and is closely tied to obesity. In one study of people seeking treatment for BED, 76% had gained five or more pounds in the prior year, and the average gain among that group was 22.2 pounds in just 12 months. Over longer periods, the trajectory is steeper: a five-year study found that obesity rates among women with BED nearly doubled, climbing from 22% to 39%.
BED is defined by recurring episodes of eating unusually large amounts of food while feeling unable to stop. To meet the clinical threshold, these episodes need to happen at least once a week for three months. But even binge eating that falls short of a formal diagnosis can drive meaningful weight gain over time.
What makes BED particularly effective at adding weight is a metabolic quirk. When someone consumes an entire day’s worth of calories in a single sitting, the body produces a dramatically higher insulin response to that meal, roughly double compared to the same calories spread across the day. Yet the body’s baseline energy expenditure doesn’t adjust to compensate. In other words, bingeing floods the system with calories and triggers outsized hormonal responses, but the body doesn’t burn more energy to offset it.
How Bulimia Leads to Weight Gain
Many people assume that purging after a binge “cancels out” the calories. It doesn’t. Research on normal-weight individuals with bulimia found a calorie ceiling after vomiting: whether someone binged on roughly 1,500 or 3,500 calories, their body retained about 1,100 to 1,200 calories either way. Larger binges don’t lead to proportionally more purging. The body absorbs a significant share of calories before vomiting can remove them.
Bulimia also sets up a cycle that promotes weight gain through hormonal disruption. People with bulimia often start at a higher weight and diet aggressively before binge-purge cycles take hold. That weight loss suppresses leptin (a hormone that signals fullness) and increases ghrelin (a hormone that drives hunger). It also lowers resting metabolic rate beyond what the loss of muscle tissue alone would explain. These changes push the body toward regaining weight, which triggers more restriction, which fuels more bingeing. The result is weight cycling, with many people gradually trending upward over months and years.
Most people with bulimia present at a normal weight when they seek treatment, which masks the fact that many were previously at a higher weight. But studies consistently show that greater weight suppression (the gap between someone’s highest weight and current weight) predicts faster weight gain over time.
Restrictive Eating Can Also Increase Weight
This is the part that surprises most people. Severe calorie restriction, the hallmark of anorexia nervosa, can paradoxically contribute to weight gain through several routes. Prolonged restriction slows metabolic rate significantly. When someone eventually resumes eating, whether through recovery or because the restriction becomes unsustainable, their body is primed to store energy efficiently. The hunger hormones that spiked during restriction don’t normalize immediately, leading to intense urges to eat that can tip into binge eating.
Research on normal-weight individuals has shown that large, sustained weight loss can itself produce binge-eating-like behavior. This helps explain why many people who start with restrictive patterns eventually develop binge eating or bulimia, both of which drive weight upward.
Atypical Anorexia and Higher-Weight Eating Disorders
There’s a persistent misconception that eating disorders only affect thin people. In reality, eating disorders are more common at higher weights. A large Belgian population study found that 12.3% of individuals with obesity met criteria for an eating disorder, compared to 5.5% of those at a normal weight. People with obesity had three times the odds of having an eating disorder.
Atypical anorexia nervosa illustrates this clearly. It involves the same restrictive behaviors, the same fear of weight gain, and the same body image disturbance as anorexia nervosa, but the person’s weight remains in the normal or above-normal range. These individuals experience the same medical consequences of malnutrition, including cardiovascular risks, electrolyte imbalances, and hormonal disruption, despite not appearing underweight. The weight history matters more than the current number on the scale: someone who has lost a significant amount of weight rapidly can be medically compromised at any size.
Night Eating Syndrome and Other Patterns
Beyond the major eating disorders, several other recognized patterns contribute to weight gain. Night eating syndrome involves consuming a large portion of daily calories after the evening meal or waking during the night to eat. Purging disorder, where someone purges without preceding binges, carries the same incomplete calorie elimination that makes bulimia ineffective at preventing weight gain. Both fall under the category of Other Specified Feeding or Eating Disorders, which share the core features of disordered eating behavior and body image disturbance.
Why Meal Timing Matters for Hormones
The pattern of eating, not just the total amount, influences how the body processes and stores food. When researchers had healthy women eat all their daily calories in one evening meal instead of spreading them across three meals, fasting blood sugar rose and the insulin spike after that single meal more than doubled. The hormone leptin, which normally follows a predictable daily rhythm to regulate appetite, also shifted its pattern in response to the binge-style eating. These hormonal changes occurred even though total calorie intake and stress hormone levels stayed the same.
This means that the chaotic eating patterns common in eating disorders, long stretches of not eating followed by concentrated intake, can alter metabolic signaling in ways that promote fat storage and increased hunger, independent of how much food someone eats overall.
Weight Gain During Recovery
For people recovering from restrictive eating disorders, weight gain is often a necessary and expected part of treatment. Weight restoration is the central criterion for remission from anorexia nervosa in clinical guidelines, because the effects of starvation are a major cause of death, largely from cardiovascular complications. Gaining weight in this context is not a side effect of recovery. It is recovery.
For those recovering from binge eating disorder or bulimia, the picture is different. Treatment focuses on stabilizing eating patterns, which often leads to weight stabilization rather than continued gain. When binge episodes decrease, the steep upward weight trajectory that characterizes untreated BED tends to flatten. Some people lose weight as their eating normalizes, while others stay at a similar weight but stop the damaging cycle of restriction and bingeing that was driving metabolic chaos.
The relationship between eating disorders and weight runs in both directions. Eating disorders can cause weight gain, and higher weight increases the risk of developing an eating disorder. Breaking that cycle requires addressing the disordered behavior itself rather than focusing on the number on the scale.