Understanding Caloric Needs in Recovery from Anorexia Nervosa

Edited by Lisa Ranzenhofer, PhD, and Janet Schebendach, PhD.

As members of the research team at the Columbia Center for Eating Disorders, we are prepared for a variety of questions from those considering our inpatient program. Among the common questions from patients is, “Why do I have to eat so much to maintain my weight?” And, “How long do I have to do this for?”

Caloric Needs Explained

The average daily caloric intake required for a typical adult to maintain their weight is in the ~2,000 range. Yet, patients recovering from anorexia nervosa often require substantially more. A high caloric requirement is at least somewhat intuitive during weight restoration. If during this phase the goal is to gain two pounds per week, then an individual would have to consume at least 1,000 calories above and beyond their usual daily requirement.

Why Nutritional Needs Remain High Well into Recovery

But why would over 3,000 calories a day be needed to maintain weight after weight restoration? While more research is needed to definitively answer this question, let’s consider activities and physiologic processes making up total caloric expenditure (metabolism).

There are three basic components of metabolism: (1) resting metabolic rate, (2) physical activity and non-exercise activity thermogenesis, and (3) the thermic effect of food.

• Resting metabolic rate is the rate at which your body utilizes energy to function at complete rest. It fuels basic vital functions like breathing and keeping warm. An outdated explanation was that people recovering from anorexia nervosa have a faster resting metabolic rate and therefore require more calories to maintain their weight. However, this hypothesis was not borne out by the data. Metabolic studies conducted by our group and others suggest that – similar to a starved person without anorexia nervosa – deprivation of food causes a drop in metabolic rate. This is likely due to loss of lean body mass and decreased rate of organ function, which both contribute to how much energy is expended at rest.

• Physical activity and non-exercise activity thermogenesis is the energy expended for anything we do that is not resting or eating. Physical activities include walking, hiking, or biking. Non-exercise activity thermogenesis includes anything else that takes energy, like writing, typing, and even fidgeting. If those recovering from eating disorders are more physically active than others, even unintentionally, then this may be an important piece of the puzzle. Increased activity – even if it is pacing or standing more often – is associated with increased caloric requirements for those without anorexia nervosa. It could be that those with anorexia nervosa need additional calories to account for extra movement.

• The thermic effect of food is the energy needed to break down the food we eat. Ordinarily, in healthy individuals, metabolic rate typically increases by about 10% after eating. This is a result of the thermic response to food. During renourishment treatment, however, the thermic response increases to approximately 30%. As individuals are doing the hard work of eating more, they may also be burning more calories breaking down that food. This exaggerated post-meal metabolic response to food may remain in effect well into their weight maintenance.

Beyond Metabolism: Other Hypotheses

What about the estimation of calorie intake? Another hypothesis potentially explaining why those recovering from anorexia nervosa require more nutrition daily relates to overestimating intake. People with an eating disorder history may know quite a bit about the macronutrient and caloric content of foods. Yet, studies show that individuals with anorexia nervosa tend to overestimate their caloric intake. Repeated overestimation could lead those in recovery to mistakenly conclude that they have met their caloric needs. This bias, compounded over time, may contribute to the need for a higher caloric prescription well into recovery.

How to Eat More

With these hypotheses about why people in recovery require more calories to maintain their weight, we begin to have some sense of the “why.” The next question may be, “how?” Weight maintenance can certainly be challenging – below are some additional articles to help:

Cognitive Behavioral Therapy for Eating Disorders

How to Establish Healthy Eating Patters in Eating Disorders Recovery

Catching the Lapse

Savoring The Journey

5 Ways to Get By with a Little Help from Your Friends

Keep Calm and Holiday On

Same Old Story? Use Cognitive Defusion to Turn the Page

Tackling Difficult Decisions Head On

Understanding the Role of Nutrition in the Treatment of Anorexia Nervosa

Project Wellness: Making Your Eating Disorder Recovery Work

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