Thursday, 2 February 2012

Healthy Weight

The term healthy weight is often bandied about, used by many friends, patients, and even other healthcare professionals. But what exactly is a healthy weight? Most people I speak to on the street thinks it's about 10 pounds or a stone less than they weigh currently. We all have an intuitive sense of what it means, though few of us will ever look like Venus or Adonis, and besides if that's our ideal isn't it based on cultural programming, rather than some physiological ideal? I'm strolling into a minefield here, and opinions run across the board, with feelings very deeply held. Rather than address the cultural and political issues of weight and eugenics, which others have done so well, I'm going to summarize the scientific evidence for what is a healthy weight, bearing in mind our definition of health. Let me apologize in advance if you can't access the full text of some of these articles, as they're behind paywalls. Lucky for me, I have institutional access.

Measuring Weight
First, a bit of history. Weight and height are plotted against each other on a nomogram, and this is used to determine an "ideal weight" for a certain height. These are still widely used in children, with centiles charted out. The concept of BMI stemmed from such nomograms. Body Mass Index (BMI) is calculated by dividing a person's weight in kilograms by the square of their height in meters. While both these methods sought to determine the normal distribution curve, they don't take account of such factors as frame size, body fat percentage, lean muscle mass. In other words, it's fairly useless on a population level. Waist circumference combined with BMI is more accurate at determining someone's risk for diabetes, hypertension, and  dyslipidemia. These in turn increase the risk of heart disease, stroke, and death. However, is focussing on weight the best intervention for lowering cardiovascular risk?

Determinants of Health/Disease
There are many determinants of health and some of these are accounted for to try to remove confounding factors in obesity studies. Poverty, gender, age, race, education, alcohol, smoking, activity levels, and nutrition are some of the common factors in studies of weight and health. Each of these plays a part in contibuting to the development of either health or disease. Yet there are few initiatives to improve socioeconomic conditions or education. Why is there a primacy of weight among the government and medical establishment? Is it perhaps so that the blame may be laid upon the individual and shaming behavior tolerated, even encouraged? I have yet to find a good reason why obesity is cosidered the great health challenge of our time, when both the BMJ and Lancet recently ran special issues addressing climate change as the biggest factor in health determination over the coming decades. It would seem that those holding the purse strings are not so interested in interventions to increase carbon awareness, as they are in policing bodily awareness.

Interventions for weight loss
While I won't argue that being massively overweight has risk for disability and psychosocial consequences, what are we doing about it? Do we simply tell those with other disabilities to deal with them on their own, or do we help them with adaptive mechanisms? We often simply tell our patients to lose weight, not an intervention I've used yet. However, most interventions don't work effectively, as a quick look through the Cochrane library's collection makes clear. The best interventions led to a mere drop of 1.3 on the BMI scale (their preferred method of measurement, not mine). The dieting industry has made its fortune on the simple premise that people desperate to lose weight will try the next fad, only to regain the weight later. This yo-yo in weight has been suggested to be more dangerous than staying fat, medically and psychologically. The interventions that have been tried cause harm, and some severely outweigh any benefit derived from them such as cardiotoxic drugs and addictive amphetamines. What's more, if even a modest weight loss leads to decreased morbidity and mortality, there must be confounding factors. I will explore these confounding factors in subsequent entries.

Perhaps a healthy weight is one where the person feels good about him or herself. While some overweight and obese people have psychological problems due to their body image, those under or normal weight do, as well. Bulimia nervosa can occur in anyone, regardless of body size. Depression is more common in the overweight. Perhaps our society's focus (with the medical establishment's endorsement) on weight is the culprit. It's better to be fit and fat than slim and sedentary. It's undeniable that being 1 point below "normal" weight is far more dangerous than being even 4 points overweight (BMI 17.5 vs 29). Perhaps there are other determinants of health we should focus on, such as nutrition and fitness. For those interested in a comprehensive overview of the interventions and evidence for weight loss, should you wish to draw different conclusions than I have, here's the NIH's booklet.

A Romero-Corral, V K Somers, J Sierra-Johnson, R J Thomas, M L Collazo-Clavell, J Korinek, T G Allison, J A Batsis, F H Sert-Kuniyoshi and F Lopez-Jimenez. (2008), Accuracy of Body Mass Index to Diagnose Obesity In the US Adult Population. Int J Obes (Lond). 2008 June; 32(6): 959–966.

Bray, G. A. (2010), Medical Therapy for Obesity. Mount Sinai Journal of Medicine: A Journal of Translational and Personalized Medicine, 77: 407–417.

Elfhag, K. and Rössner, S. (2005), Who succeeds in maintaining weight loss? A conceptual review of factors associated with weight loss maintenance and weight regain. Obesity Reviews, 6: 67–85.

I Romieu, WC Willett, MJ Stampfer, GA Colditz, L Sampson, B Rosner,CH Hennekens,
and FE Speizer. (1988), Energy intake and other determinants of relative weight. Am J Clin Nutr 1988 47: 3 406-412

Ian Janssen; Peter T. Katzmarzyk; Robert Ross. (2002), Body Mass Index, Waist Circumference, and Health Risk: Evidence in Support of Current National Institutes of Health Guidelines. Arch Intern Med. 2002;162(18):2074-2079.

Kelly D. Brownell; Judith Rodin. (1994) Medical, Metabolic, and Psychological Effects of Weight Cycling. Arch Intern Med. 1994;154(12):1325-1330.

NIH, NHLBI Obesity Education Initiative. Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. Available online:

Norris SL, Zhang X, Avenell A, Gregg E, Schmid CH, Lau J. (2005) Long-term non-pharmacological weight loss interventions for adults with prediabetes. Cochrane Database of Systematic Reviews 2005, Issue 2.

Powell, Lynda H.;Calvin III, James E.;Calvin Jr., James E.(2007) Effective obesity treatments. American Psychologist, Vol 62(3), Apr 2007, 234-246.

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