However hard we try, we cannot avoid reality: fat comes from food. If we eat more than we require for energy and biochemistry, we put on weight. If we eat less than required, we lose it - and that is that: there is nothing more that can be said on that particular subject. If people want to lose weight they should eat less and take more exercise. If they need to put it on, as in anorexia, they should do the opposite. This may not seem to be a very friendly or sympathetic thing to say, but it is unquestionably the truth.
Of course there are medical conditions such as thyroid deficiency, diabetes, Cushing's syndrome, cardiac failure or kidney failure in which weight tends to increase and there are others, such as thyrotoxicosis, malabsorption syndromes and various infections and cancers in which one may lose weight. Obviously we need to seek medical advice if we have unexpected changes in body weight. However, we should ensure that we get genuine medical advice and proper clinical investigation, with blood tests and other analyses, and that we do not get taken in by "alternative" pseudo-science that talks of "glands", "fluid-retention" and "cellulite". If there is a problem with one's endocrine glands or with fluid retention it needs to be properly assessed and these conditions are very easily differentiated from simple obesity or, conversely, the result of starvation. "Cellulite" is simply body fat -nothing more or less - and body fat is fluid at normal body temperature. "Cellulite" is not a mysterious substance that inexplicably appears from nowhere: it is body fat that comes from overeating. Getting rid of it with liposuction or various cosmetic surgery operations will not solve the problem at all. If the overeating continues, then body fat will return and, call it what you like, it is still fat.
The concept of whether one is "fat" or "thin" is largely cultural. The photographic models of today would have been considered anorexic thirty years ago - and perhaps should be today. In some parts of the world, people whom we in the West would consider grossly obese might be considered in their own countries to be healthy (free from AIDS and other wasting diseases), powerful (rich enough to be able to afford to eat that much) and often beautiful. Even in the developed world the standard medical charts, giving "desirable" or "healthy" body weight for men or women of various heights, may not take sufficient account of normal healthy ranges in body weight in people of different body type (large, medium or small frame), body muscles (varying with the level of physical exercise performed during work or recreation) and age (we tend to shrink as we get older). Furthermore, many of these charts were drawn up at a time between the two world wars when the population was generally rather undernourished. In times that are more prosperous we may be heavier but we are not necessarily less healthy, nor do we necessarily have a shorter life expectancy simply because we come outside that particular "healthy" range.
The best way of judging whether we are physically healthy in terms of our body weight is to see how far or fast we can run comfortably. If, under retirement age, you can run two miles in twenty minutes without getting particularly out of breath