The low carbohydrate case
If low fat diets are so effective, asks Dr. Atkins and other low carb mavens, then why - after 30 years of promoting low fat diets, and a massive recruitment of the American food production industry to produce low fat versions of every foodstuff - are Americans getting so fat?It's because a) carbohydrates cause obesity, and b) carbohydrates powerfully stimulate hunger, a fact that leads the poor, unsuspecting victims of the low-fat conspiracy to seek even more carbohydrates.
It works like this: When we eat carbohydrates (especially the rapidly absorbed, simple carbohydrates like sugar, potatoes, pasta, white rice, and anything made from refined flour - you know, the good stuff) we stimulate the secretion of insulin. Insulin causes glucose (the product of carbohydrate digestion) to be rapidly absorbed into the tissues for fuel consumption. Any "extra" glucose (and the vast majority of the carbohydrates we eat are not immediately needed for fuel, and are therefore "extra" calories) are quickly converted to and stored as - ta da! - fat.
Furthermore, once the glucose levels drop, the insulin levels rapidly fall in turn - and nothing promotes hunger more than a carbohydrate meal followed by a rapid spike then rapid drop in insulin levels. So, 2 - 4 hours after a high carbohydrate meal we suddenly crave (ravenously, desperately,) more carbohydrates - this minute. The cycle repeats, over and over - we eat carbos, store fat, get hungry, and seek out yet more carbos. While assiduously sticking to a low fat diet, we get fat, and as a result our cholesterol levels go up. We die.
That this sequence of events actually occurs (except the dying part, at least not for us, at least not yet) is inarguable. Thus, the scientific basis for the low carbohydrate diet seems at least as sound as that for the low fat diet, to wit: by avoiding carbohydrates, we avoid the spike in insulin levels. Since insulin is the hormone that causes our bodies to make and store fat, then by keeping our insulin levels low we are no longer fat-storing animals, we've changed ourselves into fat-burning animals. Our metabolism actually transforms, so that we primarily use our fat stores for fuel instead of ingested glucose - the fat literally melts away.
One of the nice side benefits of low carb diets is that we can actually measure this shift in metabolism; that is, we can tell whether or not we're in a fat-burning or fat-storing mode. This is because when fats are being burned for energy, byproducts called ketones are released into the bloodstream. These ketones are eliminated in the urine, and can be detected by testing the urine with special dipsticks available in any drug store. If the little brown square on the Ketostix turns purple, you're in the process of getting skinny.
Fewer scientific studies have been conducted with low carb diets than with low fat diets. This is largely because of the incredible prejudice against low carb diets that has grown within the medical community over the past 30 years. (Two generations of physicians have been weaned on the knowledge that fats are bad and carbohydrates are good.) But nonetheless, in recent years randomized clinical trials have been undertaken to assess the effectiveness and the safety of low carbohydrate diets (albeit mostly for the purpose of shutting up the troublemakers pushing those dangerous diets.) Early results from these studies have been surprisingly positive. Not only have low carb diets been shown to be effective weight loss vehicles, but also suggestive evidence has been accumulating that these diets can actually improve cholesterol and triglycedride levels. Serious doctors are finally starting to wonder if there's actually something useful there. Much more data will be forthcoming within the next year or two, but common wisdom has it that Dr. Atkins' untimely demise occurred just as his 30-year quest was about to be vindicated.
