It is well established that to have a full physiological recovery from eating disorders, weight needs to be fully restored. Goal weight is defined as the weight necessary to support puberty, growth, physical activity and psychological/social functioning.
I am often being asked: “Body Mass Index (BMI) or growth curves: what shall we follow to establish the goal weight?” The reality is that there is no consensus around this topic among health professionals. In our own journey contradicting messages were received from the family physician, the eating disorder unit at the hospital and the dietitian. There was no alignment between these bodies as to what the ultimate weight should be.
On a personal level, I consider BMI as a crude measure. In my mind, BMI should not be used as a single tool to set up a target weight for individuals recovering from an eating disorder. This is due to many reasons, some of which include:
- Some BMI calculators neglect the sufferers gender. A female and a male of the same height and weight will have same BMI. However, this is not an accurate measure due to the fact that females will usually have a higher percentage of body fat
- It does not take into account an athlete’s body; which is strong, toned and fit. An athlete’s body usually falls within an obese BMI, even though they may have a very low fat percentage
- It does not take into account bone mass. An individual with large strong bones will have a higher BMI than an individual with small bones or a lower bone density
- It does not consider individual age
- It does not consider ethnicity. For example, an Asian man compared with a Caucasian one with the same weight and height, will have a similar BMI. However, this measurement of healthy weight will be inaccurate. This is due to the fact that genetically, people of Asian heritage, are typically considered to have a smaller bone and frame size. Due to this, if both of these individuals have the same BMI, it is likely that the Asian individual will have a higher fat percentage.
It might be that your child’s BMI is in the normal range, while in fact they are under a severe weight suppression.
Research demonstrates that whenever growth curves are available they are considered to be the best method for determining an individual’s goal weight. This is because they have been proven to be more accurate than using BMI alone.
Pediatricians plot height, weight and BMI against age-based averages to generate a unique growth curve. Negative deviation from a child or adolescents weight curve is defined as weight suppression. Even in the absence of actual weight loss, the child may fall short of their optimum weight based on their unique growth curve. A child losing “only 5 kg”, may have lost even more when we closely look at their growth curve and reveal where their expected weight should be. It has been shown that deviation from growth curve (weight and/or height) can be used as a tool for an earlier detection of an eating disorder in nearly half of the patients.
It often takes up to 12 months of being at a healthy weight, before eating disorder thoughts may start to ease. One needs to remember that eating disorders may occur in people of all body sizes: This is true for small and also larger bodies. In no shape or form shall an eating disorder be used as an opportunity to avoid returning to a previous higher weight as it may prevent the child from reaching a full recovery.
Here are a few easy steps to read a growth chart and establish a target weight:
- Download the applicable growth curve chart for male / female
- Based on weight and height measurements, calculate BMI
- Plot BMI for each of the ages you have
- Establish the percentile of your child: are they at 5, 10, 25, 50, 75, 90 or 95%?
- Estimate healthy BMI by drawing a line from the individual age toward the applicable percentile chart
- Establish if your child falls at the same percentile curve. If not, calculate the deviation between the expected BMI and the actual BMI
- Use the expected BMI to calculate the expected weight and consider the difference between the expected weight and actual weight as weight suppression
- Establish target weight to be 10% higher than the expected healthy weight
- Practically, the number of kilograms your child needs to gain is the difference between the healthy weight (+10%) and your child’s weight today
If you require further assistance with this process, we can establish your child growth curve and target weight during our session.
In the event historical data is unavailable, I recommend feeding to gain weight. Do not use BMI as a stand alone tool. Focus on meal plans, support your child to overcome fear from certain foods, coach your child that eating is normal, pay attention to their physical needs, and continue with this process until they get back to a healthy state.
Remember that for someone with an eating disorder, weight restoration is essential for complete physical and mental recovery. I know it is easier said than done. Keep up on steady eating habits. Do not give up on your child. Recovery is possible.
References:
TL Bazzarre, S M Kleiner &M D Litchford Nutrient intake, body fat, and lipid profiles of competitive male and female bodybuilders. Pages 136-142 Published online: 02 Sep 2013
Butryn, M. L., Juarascio, A., & Lowe, M. R. (2011). The relation of weight suppression and BMI to bulimic symptoms. The International journal of eating disorders, 44(7), 612–61
Ingemar Swenne Weight and growth requirements for menarche in teenage girls with eating disorders, weight loss and primary amenorrhea Hormone Research in Paediatrics 2008;69(3):146-51.
Lebow, Jocelyn, Leslie A. Sim & Erin C. Accurso Is there clinical consensus in defining weight restoration for adolescents with anorexia nervosa?, Eating Disorders 2018 May-Jun;26(3):270-277.
Morgane Marion, Sylvie Lacroix, Marylène Caquard, Laurence Dreno, Pauline Scherdel, Christèle Gras Le Guen, Emmanuelle Caldagues & Elise Launay Earlier diagnosis in anorexia nervosa: better watch growth charts! Journal of Eating Disorders (2020) 8:42
Mark L. Norris, Jacqueline D. Hiebert, Debra K. Katzman; Canadian Paediatric Society, Adolescent Health Committee. Determining treatment goal weights for children and adolescents with anorexia nervosa Paediatr Child Health 2018 23(8):551
Swenne I. Weight requirements for catch-up growth in girls with eating disorders and onset of weight loss before menarche. Int J Eat Disord 2005;38(4):340-5.
Swenne I. Weight requirements for return of menstruations in teenage girls with eating disorders, weight loss and secondary amenorrhoea. Acta Paediatr 2004;93(11):1449-55.