How Likely Are You To Become Obese?

Summarized by Robert W. Griffith, MD
December 5, 2005

Introduction

Excess weight is linked to cardiovascular disease, several types of cancer, and death, as we have pointed out in these pages. It might, therefore, be useful to know what an individual's chances are of becoming obese, so that something can be done about it in good time. An analysis of information from the Framingham Heart Study provides us with this information. It's been reported in the Annals of Internal Medicine, and we summarize the findings here.

What was done

Participants in the renowned Framingham Heart Study are examined every 4 years. Those over 30 that attended exams between 1971 and 2001 and were not underweight (body mass index, or BMI, below 18.5 kg/m2) were included in the analysis. BMI data were collected on all participants up to the end of the observation period (2001), until they developed overweight (BMI above 25 but below 30) or obesity (BMI above 30), or until they died. Smoking status was recorded for each individual.

Risk assessments were made for three age categories at baseline - 30 to39, 40 to 49, and 50 to 59 years - and for short-term risk (4 years) and long-term risk (10 to 30 years).

What was found

There were 4,117 participants in the study, although only 3,710 provided data for the short-term assessment (4 years between exams). All of them were white, and 52% were women.

Short-term risk: Among those with a normal BMI at baseline, 14% t o 19% of the women and 26% to 30% of the men progressed to overweight over 4 years. (The range given allows for differing age categories.) Less than 1% progressed to obesity in the 4-year period.

Among those overweight at baseline, 16% to 23% of the women and 12% to13% of the men progressed to obesity in the short term. If those with normal and overweight BMI's at baseline were considered, 5% to 7% of women and 7% to 9% of men became obese in a 4-year period.

Long-term risk: Within 30 years, over half of both the women and men became overweight, while about 1 in 3 of the women and 1 in 4 of the men became obese. One in 10 qualified for stage II obesity - a BMI of over 35.

The effect of age, etc.: People over 50 became overweight or obese less often than younger adults. Smoking status didn't appear to make much difference.

What this means

The study shows that 16% to 28% of young to middle-aged adults with a normal BMI become overweight in the short term (4 years), and about the same proportion will go on to become obese. And in the long term (30 years) more than half will become overweight, and a quarter will become obese. Sobering numbers, indeed! And they are similar to those obtained for a Dutch population, so it's not just a USA challenge.

This study only included white people. Black and Hispanic people tend to gain excess weight earlier and more often than white. And people born more recently, figures show, tend to become overweight or obese at earlier ages. We can only hope that the efforts being made to curb excess calorie intake and to promote exercise in the young are successful.

Source

• Estimated risks for developing obesity in the Framingham Heart Study. VRS. Vasan , PMJ. Pencila , CM. Ciobain ,  et al., Ann Intern Med, 2005, vol. 143, pp. 473--480

Related Links
BMI Calculator
CDC: Obesity Trends
WHO : Obesity and Overweight

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