Conflicting reports exist on the Atkins diet, with supporters claiming massive losses from a religiously-followed low-carb regimen, opponents warning of dire consequences from ketosis, and many ordinary people claiming modest effects. The truth is that few people actually follow the Atkins diet, making the debate confusing. While discussion of ketosis may be confusing enough, the effects on most people are more subtle and more complicated than mere biochemistry.

Facts that any real analysis of Atkins must address include:

  • It's a diet
  • People "follow" diets to different extents
  • Some but not all weight loss is fat.
  • Ketosis is difficult to achieve.
  • the Western Diet is strange to begin with.
Thus, there are a variety of reasons a person might lose weight on a diet; I will present the most likely reasons a person would lose weight on the Atkins diet.

It's a diet. Not only that, it's a diet that appeals to people who have never dieted before, including more men than most previous diets as well as women who would hate to give up fat. The fact is that any diet will cause weight loss. Merely being aware of what one is eating and perhaps exercising a bit more will cause some weight loss in many naive dieters (ie new to dieting). Indeed, previous studies have shown that a diet consisting of the dieter's previously-recorded food intake generally causes weight loss - though some think this reflects more an error in people's ability to recall what they eat. Either way, any awareness of food and portion control (Atkins foods do have the benefit of coming in small portions) is clearly shown to work.

It requires thought The Atkins diet involves removing some staple foods from the dieter's repertoire of foods. This means that a bunch of foods a traditional dieter might have called "perfectly healthy" despite an unhealthy portion size must be re-evaluated.

Less snacking The typical Western snack food must be eliminated in an Atkins diet. This includes bedtime snacks and worktime snacks - excellent opportunities for weight gain. If a muffin or cupcake is given up, 300-1000 calories may be eliminated from the diet.

It's boring If fewer food choices are available, less will be eaten. Ever gotten full from a meal then eaten dessert? Variety in tastes improves appetite; Atkins (by restricting this variety) will reduce appetite.

The above factors can produce weight loss without truly restricting carbohydrate intake much. Below here are ways the Atkins diet can reduce weight that involve a real reduction in carbohydrates. Each way involves a progressively more strict Atkins Diet. Note that true ketosis is quite hard to achieve, since typical Atkins foods such as cheese and meat do contain some carbohydrates.

Fat is filling In the Western diet, carbohydrates are generally from white rice, white flour, potatos, corn syrup, etc. They are quickly digested and are therefore eaten in large quantities. The best solution is to eat more complex carbohydrates, which are more nutritious, more filling per calorie, and reduce the risk of cancers and heart disease. Fat is filling like complex carbohydrates, although without these other benefits. By switching away from simple carbohydrates to fat, a dieter can lose weight without becoming hungry as mere portion control would do.

Water weight: Without enough carbohydrates, the body cannot replace stored carbohydrates. The liver stores carbohydrates as glycogen, along with water due to oncotic pressure. Thus, about 10 pounds of water can be lost from the average liver by losing this glycogen. Of course, the glycogen is highly useful in aerobic exercise, since it's used for gluconeogenesis to send glucose to the exercising muscles.

Ketosis causes nausea. If a dieter is particularly strict about reducing carbohydrates, ketosis can be achieved. The body must have a certain amount of glucose or ketone bodies around, since these are the only possible foods for the brain. If there are not enough carbohydrates to provide glucose, ketone bodies will be produced from proteins (and to a lesser degree fats, since during fat degradation as pairs of carbons are removed these cannot be used; only the odd 3-carbon leftover can be used.) These can feed the brain, but cause acidosis and ketosis of the blood; this causes nausea and reduces appetite.

Degradation of the body could be required. If a person were truly insane about carbohydrate reduction, they would have to give up standard low-carb fare such as cheeseburgers sans bun in favor of, say, pure olive oil. Such a person would break down existing proteins in their muscle in order to produce ketone bodies to keep the brain alive. This is not the typical reason for weight loss in a normal dieter.

Summary: People claiming weight loss from the Atkins diet could probably lose the weight from a healthier diet involving more vegetables and complex carbohydrates. Nevertheless, the typical dieter does not follow Atkins or any other diet well, and if the question is whether the average Western diet would be slightly improved by eliminating hamburger buns, the answer would be yes.

Please note that my observations regarding the frequency with which dieters actually follow their diets is based on experience with St Louis city hospitals. In other cities and settings, it is possible that dieters are more motivated than this.