Does the body mass index get more attention than it deserves?

Ann Silversides

CMAJ 199;161:72

The young woman who had approached Seid was heavier than average, and volunteered that her food intake had been obsessively controlled since she was a child. One of the happiest times in her life occurred several years ago when, before it was fashionable, she took up weight training. She loved going to the gym and became very strong, she said. She didn't explain why she'd stopped.

Like this overheard conversation, many of the presentations at this 1-day conference on dieting, obesity and weight loss raised interesting questions and issues, but they did not answer the questions or attempt to reconcile the issues. A case in point was a debate involving a psychiatrist, internist and diet-industry critic. The topic? "Dieting as a necessary treatment option for obesity."

Since 1979, psychiatrist Jeanne Randolph, an assistant professor at the University of Toronto, has worked with the "super obese" — patients with a BMI (body mass index) of 30 or more. Many have developed diabetes, hypertension and osteoarthritis because of their condition.

Randolph stressed the "relentless suicidal undercurrent" among her patients, and said personal factors common to them include a traumatic life change (assault, death, car accident) and an identity centred on compulsive caregiving. For her patients, food is both a friend and an enslaver, and their large bodies are a source of protection and persecution. Randolph said many were thrown into "weight loss crisis" whenever they lost noticeable amounts of weight.

On the other hand, internist Ted Monchesky of the Oshawa General Hospital stressed the heightened health risks posed by obesity and emphasized the importance of slow, steady weight loss. He noted that people with a BMI over 29 had a 3.5 to 4 times higher risk of developing cardiovascular disease than people with a lower BMI. He also argued that prescription drugs can help achieve weight loss, although those now on the market should be used only for short periods and with careful monitoring. "Our future lies with future medication," Monchesky said.

However, Frances Berg — a critic of dieting who edits an American publication, Healthy Weight — said irreversible heart, valve and lung damage had been linked to some diet drugs. "In obesity treatment and losing weight, everything works short term and nothing works long term," Berg warned. Long-term weight loss does not occur until after at least 2 years, but almost all studies of weight-loss techniques use "impeccable but irrelevant" 6-month data. She added that weight-loss programs typically take credit for short-term weight loss, but blame individuals for subsequent weight gain. She said US$30 billion to $50 billion is being wasted each year in the US on such treatments.

The 3 distinct perspectives left some conference participants puzzled. Dieticians and psychiatrists wondered out loud whether they should or should not promote weight loss, but they did not get a definitive answer.

Debate moderator Dr. David Goldbloom, physician-in-chief at the Centre for Addiction and Mental Health in Toronto, noted there is a genetic, emotional and social perspective to obesity and "it is not the exclusive domain of any one of these; we need to tailor our approach to the individual."

He warned against placing too much importance on BMIs, since individuals with the same BMI could have quite different genetic endowments, living circumstances and personal habits (smoking, exercise, alcohol consumption) — all of which would significantly affect their health risks. But he said the BMI, in an era that endorses the idea of personal control over health, may be imbued with more significance than it deserves simply because it is so visible.

Obesity Canada, a new organization that focuses on research and education, held its inaugural meeting in April. Charter members include nearly 100 dietitians, nurse educators, researchers, physicians and representatives from Health Canada and other organizations. Obesity Canada aims to improve Canadians' health through research and education about obesity and "its clear health consequences," stated Dr. David Lau, the president. The group's Web site, www.obesity.ca, is expected to be launched this summer.

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© 1999 Ann Silversides