The crusade on overweight and obesity now expanding worldwide is poised to change drastically those traditional ways of life that prevail in most developed countries countries that nevertheless have witnessed a near doubling of life expectancy in little more that a century, parallel to a steady increase in average body weight. Common sense would expect epidemiological studies of obesity and overweight to be based not on nebulous guesses but on actual measurements with sufficient and testable precision, on measurements that have measured what is said to have been measured and not something else, and on conclusions strong enough to make a difference and repeatedly consistent. In reality, these requirements are never met in epidemiological studies of overweight and obesity.

The majority of those studies do not actually measure overweight or obesity but rely on what people report offhand about their own height and weight during telephone interviews or by responding to written questions. Even when height and weight may be measured, any excess of body mass over an arbitrary threshold of normalcy is assumed to be fat when in reality it could be muscle, water, or heavy bones. If an overweight person dies of lung cancer it is not possible to say that overweight was the cause of death without asking if the person was a smoker, exposed to asbestos or radiation, or to scores of other possible hazards for lung cancer. Still, no study has adequately inquired about the so many possible causes of death and disease to which study participants could have been exposed. Ethnic, behavioral, occupational, environmental, physical fitness, and many more differences could easily bias the results and were never adequately addressed by epidemiological studies. Thus, as could be expected, studies often come to divergent conclusions.

Is obesity truly an epidemic? In reality, reports indicate that while a large majority of people may have gained very few pounds an apparently healthy gain - over the last decades, it is only a small fraction of obesity-prone subjects who have registered excessive weight increases. The same conclusions hold for children. This means that by far the majority of people have been impervious to obesity and self-regulate their weight remarkably well. In fact, more recent information indicates that the trend of small weight gain for the majority of people may be coming to an end, reflecting observations that the average caloric intake my have been stationary or decreasing.

The claim of an obesity epidemic rests on statistical equivocations, and most of the problem lies in how overweight and obesity are measured and analyzed. The common method is a combination of weight and height measures called the body mass index (BMI), for which an arbitrary normalcy standard of BMI 25.0 has been set. Most studies assess average BMI values for segments of the BMI range of values, so that the average for a group of people in the segment of BMI 25.0 to 30.0 will be skewed upward by the presence of truly obese subjects at the high end, even though people at the low end of the segment might be quite normal. Clearly, what needs to be done is to analyze segments of the BMI range that are homogeneous for the characteristics that count, namely mortality or disease rates. However, to achieve a realistic segmentation of the BMI range it will be necessary first to define normal BMI ranges for different groups of subjects, depending on age, sex, ethnicity, prevalent diseases, and many other characteristics: a daunting task whose incompleteness casts heavy uncertainties on claims about overweight, obesity, and their possible consequences.

Even when normalcy ranges were to be known, the task of counseling dangerously thin or obese individuals would still be daunting, after considering the problematic record of bariatric medicine and surgery, and the pitiable histories of self-correcting attempts by obese and overweight people. The literature is replete with reports of the dangers of losing weight even under supervised regimens.

What is an intelligent person to conclude? A clear impression is left that epidemiology is truly powerless in this case, given the barrage of heavyweight endorsements from all sort of professed authorities. For overweight and obesity the risk differentials over the middle range of BMI values are usually less than 1 and could be easily trumped by questionable measurements and many uncontrolled biases and confounders. It is only for very thin and definitely obese people that higher risks are recorded and raise legitimate concern.

Lest these remarks and other to follow - be misconstrued, the analysis in the following pages should bring confirmation to anyone willing to look at the evidence with an open mind and eyes. It will not be an analysis in the technical sense which would be useless for the purpose at hand but a survey of the uncertainties and inconsistencies that affect the studies. Fortunately, the construct of epidemiology is not rocket science and is fully accessible to any person of average education, most epidemiologists included.