Obesity is now classed as a disease according to a recent decision taken by the American Medical Association (AMA)which is the official body representing the medical profession in the USA. This decision was reached despite the fact that the AMA’s own Council on Science and Public Health had concluded that:

Without a single, clear, authoritative, and widely-accepted definition of disease, it is difficult to determine conclusively whether or not obesity is a medical disease state. Similarly, a sensitive and  clinically practical diagnostic indicator of obesity remains elusive.”

The report went on to state that

“…given the existing limitations of BMI to diagnose  obesity in clinical practice, it is unclear that recognizing obesity as a disease, as opposed to a  “condition” or “disorder,” will result in improved health outcomes.”

The reality is that obesity as determined by BMI is totally inadequate as an indicator of a person’s health status as explained in Blogs 10, 11 and 12. For any given BMI value there is a wide variation in life expectancy. These conclusions have been confirmed recently in a meta-analysis which was published in the Journal of the American Medical Association at the beginning of this year (1). After eliminating any studies which were considered dubious, the research team was left with data from 97 different investigations, involving 2.88 million individuals, of which records were available for 270,000 who had died. The results (Table 1) show that those in the Overweight and Obesity 1 had a lower death rate (longer life expectancy) than those who were in the Normal (ideal) BMI. It must be emphasised that this is in full agreement with many earlier investigations (See Blogs 10, 11 and 12). With such a large number of individuals involved we can be confident that these conclusions are reliable and will stand up to rigorous examination.


BMI Relative death rate
20-25 Normal 1.00
25-30 Overweight 0.94
30-35 Obesity category 1 0.95
>35 Obesity categories 2   and 3 1.29


What this means is that those who are Overweight or Obese category 1 are considered to be suffering from a disease even though on the evidence of BMI alone there is absolutely no reason to believe they are at a greater risk of dying than those in the Normal BMI. In fact the evidence above shows these people have a lower death rate than those regarded as Normal.

The misrepresentation of the research on the relationship between body weight and health goes back a long way. In 2004 in his book “The Obesity Myth” Paul Campos analysed the evidence which was used as the basis for the conclusion that there is a strong international consensus among scientists that overweight( BMI over 25 ) and obesity are major contributors to early death(2). Essentially there were 4 major studies involved.

In the Nurses’ Health Study (3) there was little or no risk of increased mortality associated with body mass among the 82% of women who had BMI s between those regarded as Normal/Ideal in the range of 19.0-24.9 and those in the Overweight range of 25.0-31.9. In fact the women with the lowest death rate were actually heavier than average with a BMI of 25.0-26.9, which is of course deemed to be Overweight. Campos concluded that the data from the 4 studies certainly did not support the official line. What the evidence demonstrated was that although very fat and very thin people have a reduced life expectancy, there is little difference for those with a BMI between 20 and just over 30. Furthermore the lowest mortality is invariably found in those who are in the Overweight category. This means that according to official US guidelines the average person is better off being 25 to 35kg “overweight” than 3 kg “underweight”.

It is abundantly clear that the decision taken by the AMA is not based on reliable evidence of any kind. Nevertheless the significance is of course is that patients who do not have a BMI which is in the Normal range are likely to be advised that some form of treatment is required. This may include:

  • Losing weight even though the success rate is very low and is likely to result in reduced life expectancy (See Blog 31)
  • Prescription of various drugs
  • Bariatric surgery

In view of the lack of evidence that being overweight or mildly obese increases the risk of dying it follows that there is absolutely no need for any treatment. There is every possibility of harm not to mention the unnecessary anxiety and worry caused by such action.

Although most of the information cited here has originated from the USA, exactly the same approach applies in the UK as will be obvious to anyone who logs on to the NHS Choices website (4).

The key issue is actually fitness, not fatness (See Blog 12). People who are sedentary and have a poor standard of physical fitness are at a much higher risk of developing chronic disease and reduced life expectancy than those who are reasonably fit irrespective of BMI. For those who have a sedentary lifestyle, there is no doubt that by taking some exercise such as walking for 30 minutes every day will result in an improvement in health status. However it is important to recognise that increased activity is unlikely to result in any significant loss of weight.

It is important to appreciate that if a person with excess body fat has other symptoms such as high blood pressure, raised blood sugar (diabetes or pre-diabetes) and raised blood triglycerides(fat) then there is definitely cause for concern as the risks of heart disease and certain diseases will be increased. Usually these can be alleviated or eliminated entirely by reducing the consumption of sugar and other carbohydrates (See Blog 35).

A cynic might be forgiven for concluding that the reason this advice is given so rarely is because no-one makes any money from the implementation!!!


  1. K M Flegal etal (2013) Journal of the American Medical Association 309 (1) pp71-82
  2. P Campos (2004) “The Obesity Myth: Why America’s Obsession with Weight is Hazardous to Your Health” Gotham Books New York pp 13-19
  3. J Manson et al (1995) New England Journal of Medicine 333 (11) pp 677-682
  4. http://www.nhs.uk/Conditions/Obesity/Pages/Introduction.aspx