Retrospective #284: The A to Z Weight Loss Study: a Randomized Trial

A dear reader – and I mean that sincerely because I write this blog for my readers – was disappointed (upset, actually) that I said, “…if you are insulin resistant, as almost all fat people are…” Okay, “fat people” is an inflammatory phrase, and I rarely use it, but that is not what upset Valerie. It was an assumption, and a slight exaggeration that I made, that did it. She concluded: “I wish your ‘nutrition debate’ weren’t so one-sided.”

Valerie’s frustration (and upset) is a result of my writing about two overlapping and related but different phenomena: the co-incident epidemics of diabetes and obesity that have come together in the last 40 years. It all began with the publication of the Dietary Goals for Americans in 1977, produced by staff of a Select Committee of Congress, and the Dietary Guidelines for Americans in 1980, first produced in 1980 and then every 5 years by the USDA and HHS. These government attempts to tell the population what to eat have had an enormous impact of our health and wellbeing.

The combination of Type 2 diabetes and obesity is so prevalent today that the word “diabesity” has been coined. However, as Valerie points out, not all “fat” people have Insulin Resistance (IR), a requisite condition for progression from a normal glucose metabolism to Impaired Glucose Tolerance (IGT), Impaired Fasting Glucose (IGT), and then to a diagnosis of incipient Type 2 Diabetes Mellitus (T2DM). That is the Natural “History” of Type 2 Diabetes. Apparently, Valerie is obese but not Insulin Resistant or therefore by definition not a Type 2 diabetic or Prediabetic. Lucky her.

So, I give Valerie her point: There are plenty of slim people with insulin resistance and plenty of fat people (about 20%) without insulin resistance…” Apparently Valerie is one of the 20%. But I will contest her assertion that “fat people without insulin resistance” did not benefit from the “A to Z diet trial.” She states erroneously that “low-carb diets didn’t help [them], if you remember the A to Z diet trial.”

The A to Z Diet Trial, was a “Twelve-month randomized trial conducted in the United States from February 2003 to October 2005 among 311 free-living, overweight/obese (body mass index, 27-40) nondiabetic, premenopausal women.” By definition that means that the participants did not have Insulin Resistance. It was a “Comparison of the Atkins, Zone, Ornish, and LEARN diets for change in weight and related risk factors…,” published in JAMA in July 2007.

The following are excerpts from the ABSTRACT:

“MAIN OUTCOME MEASURES: Weight loss at 12 months was the primary outcome. Secondary outcomes included lipid profile (low-density lipoprotein, high-density lipoprotein, and non-high-density lipoprotein cholesterol, and triglyceride levels), percentage of body fat, waist-hip ratio, fasting insulin and glucose levels, and blood pressure.”

“RESULTS: Weight loss was greater for women in the Atkins diet group compared with the other diet groups at 12 months, and mean 12-month weight loss was significantly different between the Atkins and Zone diets. Weight loss was not statistically different among the Zone, LEARN, and Ornish groups. At 12 months, secondary outcomes for the Atkins group were comparable with or more favorable than the other diet groups.”

“CONCLUSIONS: Premenopausal overweight and obese women assigned to follow the Atkins diet, which had the lowest carb intake, lost more weight at 12 months than women assigned to follow the Zone diet and had experienced comparable or more favorable metabolic effects than those assigned to the Zone, Ornish, or LEARN diets…”

So, just to be perfectly clear, non-diabetic, premenopausal overweight and obese women who ate the diet with the lowest carbohydrate intake lost the most weight and had the best improvement in related risk factors.

The low-carb diet DID help “fat people without insulin resistance,” and by a large margin. After 12 months, the Atkins cohort actually lost 3 times as much weight at the Zone cohort and twice as much as the average Ornish and LEARN dieter and had “comparable or more favorable metabolic effects” than those on the Zone, Ornish, or LEARN diets.

I’m sorry to have to come down so hard on this point, but it must be made clear to all my readers that low-carb diets DO WORK (for the vast majority of people, if I have to hedge). If you haven’t given it an honest try, you really should.