Setting a Target Weight: An Arbitrary Exercise?

Achieving a healthy weight is a major goal of anorexia nervosa treatment. Indeed, a healthy weight is often seen as a prerequisite for psychological recovery. The fact that weight restoration is a crucial component of recovery is uncontroversial, the problem arises when it comes to determining what constitutes a healthy weight. How are ideal, optimal, or goal weights set? And who gets to decide?

Despite its recognized importance, there’s surprisingly little consensus on how target weight should be determined. Moreover, as Peter Roots and colleagues found out, when it comes to inpatient treatment centres in the UK and Europe, there is little consistency too.

In a study published in 2006, Roots et al. examined how treatment centres determine, monitor, and use target weight in the treatment of adolescents with anorexia nervosa. They also wanted to know the centres’ expected rate of weight gain, how often patients were weighed, who was involved in setting the target weight, and how target weights were used in the “therapeutic process and discharge planning.” They sent out questionnaires to 28 specialist inpatient ED services (17 in the UK and 11 in other European countries).

Twenty-one treatment centres responded. Non-UK respondents included centres in Denmark, Finland, Holland, France, Germany, Sweden, Spain, and Ireland.

I’ve summarized the main findings below.

How many treatment centres set target weights?

Out of the 21 centres, 18 set weight targets: 10 set target weights and 8 set target weight ranges. 

How and when are the weight targets set (out of the 18 that set weight targets)?

Five set target weights prior to admission whereas nine  did so on admission. Sixteen took into account age-related norms when setting the targets by looking at the weight:height ratio (9), BMI percentiles (5), and both (2).

Twelve set the targets according to service policy (what that means was not specified), four set them in negotiation with the patient (usually after a period of inpatient treatment), and two by considering individual variables such as parental and/or pre-ED weight. Interestingly, two services emphasized “the importance of not negotiating the target weight.”

So, out of the 21 services there were fifteen different responses with regard to how target weights were set (see Table 1 below). Note that three did not set target weights and two did not provide information on how they calculate target weights, which means that out of 16 responses, only two were the same.

What is the expected rate of weight gain?

Services ranged from 0.3 – 1 kg per week (~0.6 – 2.2 lbs) per week; most expected a consistent rate of weight gain throughout (~0.8 kg or 2 lbs per week).

The table below details the different ways that various services set their target weights and what those targets “mean” for a 14-year-old, 160 cm tall female (that’s around 5’3″).

Interestingly, a third of the services (7) used pelvic ultrasound scans to “inform progress” and some of the services used the information gained to alter, if necessary, the target weight. I thought that was interesting because I wouldn’t have predicted it to be so popular. Indeed, I had never heard of using pelvic ultrasounds to inform target weight until I was researching around before writing this post and came across this post:  Using Ultrasound to Predict Weight Regain in Anorexia Nervosa and Carrie’s post here.

Weight Gain and Discharge

Given that weight gain is an important component of treatment, it is not surprising that it is also an important factor influencing discharge. Out of the 21 centres:

• In nine places, discharge depended on reaching the target goal/goal range, and seven required a period of weight maintenance (ranging from 1 – 6 weeks)
• Eight, in addition to weight, also relied on “parental confidence” and “patients taking responsibility for food intake” when deciding on the appropriate discharge time
• Two mentioned including “emotional or psychological change” as being important factors in determining discharge, with one of these reporting moving away from using target weights and focusing on issues of emotional regulation instead

WHAT DOES ALL OF THIS MEAN?

For one, the lack of consistency among ED services in determining the target goal weight, expected rate of weight gain, and discharge criteria means that a 14-year-old girl weighing 36 kg on admission can be discharged at:

• a BMI of 16.5 after 13 weeks of treatment in one centre (~0.5 kg/week),
• a BMI of 18 after 10 weeks of treatment in another centre (~1 kg/week),
• a BMI of 18 after 33 weeks of treatment in a third centre (~0.3 kg/week),
• and a BMI of 21 after 20 weeks of treatment in the fourth centre (~1 kg/week)

As Roots et al. point out, the target weight for this patient can vary by over 11 kg (that’s over 24 lbs) and the total length of admission can vary by 23 weeks — and that’s just among the treatment services evaluated in this study.

In a study of Australian dietitians, Rocks et al. (2013) found similar variability in how target goal weight was determined:

Twelve dietitians reported that weight targets were commonly set for inpatients in their facility and this was usually determined by the multidisciplinary medical team. The remainder of practitioners stated that weight targets were based solely on the needs of an individual patient. The target weights were defined using: target weight (10 dietitians), target body mass index (8), or target weight range (9) or target BMI range (8). The specifics of weight targets were commonly dependent on individual characteristics, for example, normal weight for height percentiles, developmental stage of inpatients, and the treatment plan and management policies of the treatment facility. However, a minimum of the 10th and 15th BMI percentiles, the 50th BMI percentile, and an adult BMI of 20 or 21–25 (a healthy weight range) were also quoted as targets used in practice.

MY THOUGHTS… 

Target goal weight is a funny thing. On the one hand, recovery means moving away from focusing on weight but on the other hand weight restoration is important (and many would argue necessary) for psychological recovery. Moreover, treatment services have to have discharge criteria — after all, we don’t have unlimited resources and we do want to offer treatment to as many individuals as possible (I think, anyway). New patients have to be admitted and others have to be discharged eventually.

Besides, as I’ve written before, inpatient treatment has its own drawbacks, so sticking around too long in an IP or residential setting may not be a good idea either. (It depends on a lot of factors of course.) That said, a low BMI at discharge is associated with relapse and poor long-term outcome (here, here, here, here, and here; some of these show that a higher BMI at discharge is predictive of a favourable outcome).

Finally, although weight restoration and resumption of menses are important, the focus on achieving a goal weight can become counter productive not only because it can make patients feel like the only thing that clinicians care about is their physical recovery (and not psychological state) but also because patients themselves can become obsessed with maintaining that goal weight (and not a pound more). That, I think, is still quite disordered,  particularly considering how arbitrary these goal weights can be and how wrong clinicians can be about what they consider a “healthy” weight (see example here and here). (Though, to be fair, it is probably less physically damaging, which is not nothing.)

BMI values provide a quick and easy way to assess physical recovery. I think all of us — patients, caregivers, and clinicians alike — want to believe that a healthy weight = a healthy state. We all know it is not true, but we want to believe it is. Achieving that healthy state usually takes a lot (sometimes a loooooooooot) longer than achieving a healthy weight, and arguably , a lot of that progress must be made outside of the hospital (or residential treatment) walls.

Still, discharging patients when they are only at their target weight because they’ve been practically forced to gain (and are already making plans to lose it), when they haven’t yet reached a healthy weight, or when they are told that a certain weight is healthy when it isn’t healthy for them is not a good foundation for recovery post-inpatient (to say the least).

Roots et al. pick up on this:

As reported previously (Gowers et al., 2002), psychological factors are much less important for monitoring progress and deciding on discharge. This is surprising given the psychological basis of the condition and the well-documented frequency with which patients restrict their dietary intake as soon as they are discharged.

It is a bind, really. Achieving a healthy weight is important but determining what is a healthy weight (especially for a growing adolescent) is hard. Achieving a healthy weight is important for psychological recovery but focusing too much on a weight goal (especially an arbitrarily determined weight goal) is counter productive for recovery because it can fuel disordered thoughts and take time away from focusing on psychological recovery.

But goals are important and weight is an easily quantifiable goal. Besides, I’m not sure how well I would’ve taken to the concept of just letting my weight stabilize at whatever point is healthy for it… to “just eat” — and I wanted recovery and fought for it. But it was still scary. Trusting my body is a concept I am still getting used to — even after maintaining the same weight and eating really well for quite a while. 

Roots et al. conclude with the following:

Whatever the theoretical issues about setting an ideal weight, inpatient services may be choosing to make unilateral decisions on target weight setting based on population norms rather than taking an individualised approach because they feel this is more therapeutic. Giving patients a clear non-negotiable, relatively easily quantified goal to work towards may allow them to better concentrate on their treatment. However we should be aware that targets set may not necessarily be valid markers of recovery. The wide variation in target weight setting, the implications for length of hospital admission and therefore cost, highlighted in this study may give cause for reflection on the validity of the choice of in-patient targets weights

I don’t think there’s a perfect solution for these dilemmas, but I do think it is important to think about them anyway.

References

Roots, P., Hawker, J., & Gowers, S. (2006). The use of Target Weights in the Inpatient Treatment of Adolescent Anorexia Nervosa European Eating Disorders Review, 14, 323-328 DOI: 10.1002/erv.723