The fact is that there is no one carb level that will be best for everyone. Atkins talked about "metabolic resistance", others talk about "sugar sensitivity" or "carbohydrate tolerance". They all essentially are driving at the same thing: Different bodies have different abilities to handle carbohydrate, and the trick is to figure out what is best for your body. Most of the reduced-carb diets try to address this issue by offering ways to better individually customize the diet.
The GoalThe goal is to find the highest carb level where the individual will 1) lose or maintain weight and 2) not have cravings which will drive him or her to overeat. These cravings are a very important marker, and almost every low-carb diet book from Atkins to South Beach talks about it. It is one of the most striking features of low-carb diets -- that people no longer find themselves wanting to randomly munch. Being free of those urges is so liberating that it turns people into devoted followers of carb reduction. Other positive signs of eating the correct carb level are increased energy and mental alertness. Also, of course, people who are diabetic or prediabetic can and should monitor how what they eat is affecting their blood glucose.
Atkins calls the point at which a person can eat the most carbohydrate while still losing weight and getting the other benefits of the diet their "Critical Carbohydrate Level for Losing" ("CCLL") Agatston of the South Beach diet doesn’t have a name for it, but he recommends that dieters in Phase 2 of his plan gradually raise their carbohydrate level until they experience cravings, and then back down.
Getting to the GoalAtkins and Agatston both require a highly restricted initial phase of their diets. It is these phases that have drawn the most criticism. It is legitimate to ask whether it is necessary to cut carbs this much, even for a short time.
The fact is that we are beyond the realm of scientific research on this point, and are into more of an art that needs to be individually customized. The way I look at it is this: People who are sensitive to carbohydrates are on a continuum. Some will benefit from small reductions in carb, while others need a larger reduction to experience the benefits. If they all go on a slightly carb-reduced diet, a small percentage of them will reap the benefits. If everyone goes on a highly restricted diet, they will almost all get the benefits of carb restriction, but they may also have some negative effects from the diet itself, especially in the first week. So the trick is to find a way to help each person zero in on the best level of carb intake for them. To me, as to Atkins and Agatston, finding the highest carb level where the benefits can be achieved is a good goal. But is cutting back severely first the best way?
Different Strokes...It probably is the best way for some people. But it seems likely that most people can still receive the benefits by starting at a higher carb level, and avoiding some of the problems. While Atkins starts people at 20 grams of daily carbohydrate, the Eades of Protein Power say 30 grams, Diana Schwarzbein of The Schwarzbein Principle says at least 60, the Zone says 100 to 150, and Sugar Busters would probably be around 140 to 200 grams. All of these are considerably under standard nutritional advice, which is generally around 250 to 300 grams of carbohydrate daily (depending upon calories and other factors), and certainly you hear people on all these plans who are saying essentially the same thing about the positive effects –- decreased cravings, increased energy, etc.
So how do we start? I recommend that people start a little higher than Atkins recommends, and this is why: At 20 grams of carb per day, a significant number of people experience negative effects. It is also difficult to get the full range of nutrients on 20 grams of carbs per day. However, when you raise the carb allowance to 30 or, better yet, 40 grams per day, it becomes much easier to create fully nutritious meal plans. Additionally, at higher carb levels, people are less apt to get bored, because they can eat a greater variety of foods. Then, they can increase from that point, just as Atkins and Agatston suggest. Carb cravings or weight gain is a sign to back down to a lower level of carbohydrate, which give the maximal benefit for the least discomfort. That produces a way of eating that people can live with, rather than a “crash diet.”