Reproduced by kind permission of F.E.A.S.T. (Families Empowered and Supporting Treatment of Eating Disorders)

Setting Target Weight

After an eating disorder diagnosis, it is important to determine whether the patient’s disordered eating behaviors have artificially changed body composition and weight. This allows the treatment team to make a plan for how to achieve nutritional rehabilitation, which is a critical first step in recovering from an eating disorder. This restoration of medical health is important for regaining mental and medical stability. In anorexia, most patients lose muscle and necessary fat stores as well as deplete vital organs, bone, and tissue as the body tries to cope with malnutrition. With bulimia, body weight may be in the normal range, but the inconsistency of nutrition can affect metabolism and growth.

No Common Standards

Unfortunately there is no common standard among clinicians or fields for setting target weights and ranges. In addition, many insurance carriers cover only emergency conditions so patients are released or care is ended before true recovery. Failure to reach and maintain a metabolically healthy body stalls recovery and leads to relapse and chronic illness. 

Parents need to know: target weights and ranges are not an exact science, each patient will have a healthy weight range that is unique to their biology and their development, weight ranges change over time, maintaining a weight range lower than metabolically healthy for the individual keeps the patient from full mental recovery.

One Clinician’s Guide to Setting Target Weight Ranges

While setting target weight ranges is not an exact science, it is possible to come up with some very good initial figures by following some basic guidelines. The following paper, written by F.E.A.S.T. Advisory Panel member Julie O’Toole, MD, MPH, is an excellent guide for parents and pediatricians to use when assessing a recently diagnosed patient: Determining Target Weight Ranges and Ideal Body Weigh.

Lifetime growth charts

Many clinics now use lifetime height and weight charts to determine where a patient would have been had the illness not altered growth. This is especially helpful for patients whose weight is considered “normal” in terms of BMI but mental or other measures indicate a problem. It is possible for a person to have a “normal” BMI but still be significantly underweight for his or her own frame and physiology. Parents can plot their child’s growth on the following charts, or obtain growth records from their child’s regular physician:
CDC Growth Chart for Girls up to age 20
CDC Growth Chart for Boys up to age 20

Ideal Body Weight (IBW)

Although calculators exist on the Internet for IBW, there is no agreed upon standard for calculation. The Mclaren, Moore, and BMI calculations (below) fail to take age, development, and genetic factors into consideration.


Body Mass Index is a controversial measurement that has become ubiquitous in modern society. A ratio using height and weight, BMI does not take into account body composition or whether the patient is healthy. BMI is a population screening tool that offers a view to where someone’s weight/height compare to others. It does not differentiate between fat/muscle mass, so athletes will often have BMI’s deemed: “overweight.” By definition, the BMI curve allows for perfectly healthy people on the high and the low end of the scale – it also tells nothing about the actual health of the person it is measuring. It is especially difficult to use BMI to evaluate growing children as they go through growth spurts and may be delayed from illness. Many eating disorder clinics and clinicians do use a mid-range BMI standard (20-22) as an initial goal, reassessing as patient’s health improves.

Other Measures of Health Status

Hormone levels

Malnourishment, even small amounts less than needed, causes the body to cease non-essential functions. Fertility and sex drive are some of the first functions that the body and brain shut down to save energy. For girls, resumption of regular menstruation can be an indicator of maintaining sustainable weight and body composition. For boys the signs are more difficult to discern, but include a resumption of nocturnal emissions and interest in sex.*Special note on the use of birth control pills in eating disorder patients.

Family History
Healthy body composition, weight, and height are largely determined by genetics. While tall blonde parents may occasionally give birth to short brunettes, most of the time children look – and at healthy weights are shaped – like their relatives. Twins raised separately generally have similar adult weights, for example. Family history is often used to help determine whether a patient is in a normal weight range and target weights should take genetics into account.

Body composition analysis

Some clinics use body composition analysis in determining whether a patient is maintaining a healthy weight. This calculation of lean body mass and fat can be helpful in assessing weight goals.

Indirect Calorimetry

Measuring Resting Energy Expenditure (REE) is one way to determine the metabolic rate and use of calories in a recovering patient. This is measured through direct or indirect calorimetry

Pelvic ultrasound and menstrual status for female patients
For female patients, an ultrasound of the ovaries can determine whether the patient is ovulating, and give an indication of reproductive health. Although menstrual status has long been used as a measure of severity of anorexia, it has lost favor as a diagnostic tool. Patients with chronic malnutrition have in significant numbers continued to menstruate, and patients who are fully recovered may still not resume normal periods. Click here for a protocol for this approach.
Vital signs

Some physicians find it helpful to use vital signs like heart rate and orthostatic blood pressure changes to determine whether a patient has stabilized and is functioning normally. Other indications include: normal body temperature, coloring, pulse, and how fast skin pressed with a fingernail returns to a normal color (capillary refill).

Blood tests
It is common for clinicians to do blood tests during diagnosis and evaluation. However, parents should not be relieved by “normal” lab reports. Sadly, blood tests are not a good indication of health: the body compensates for malnutrition and a patient can have “normal” measures almost until death. Tests for levels of sex hormones are often done to determine whether levels suppressed by malnutrition have returned to normal levels (this can take months after reaching and maintaining a healthy weight range.)

Emotional stability
Many parents report developing an intuitive sense of a loved one’s weight range stability through behavior. As a patient settles into physical health there are also subtle signs of emotional stability, flexibility, and increased ability to reason. Likewise, parents report knowing when things have slipped out of range through behavior and attitude.

Courtesy of F.E.A.S.T.



Charlotte Bevan, wife of a farmer, mother of teenagers, breast cancer survivor and parent advocate Secretary F.E.A.S.T. UK, Expert Carer, Echo Project, Institute of Psychiatry, talkhealth and Mumsnet Blogger

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