There are some new clues to weight loss and weight gain that appear to explain some of the problems we have interpreting results from research studies that address this issue. So many times, there are conflicting results and conclusions more than likely due to the complexities of weight loss and weight gain. Dr. Christopher Gardner directed the Stanford diet study to help us understand these complexities. He is the director of nutrition studies at the Stanford Prevention Research Center and associate professor of medicine at Stanford University.
The study was published in the March 7, 2007 issue of the Journal of the American Medical Association entitled Comparison of the Atkins, Zone, Ornish and LEARN Diets for Change in Weight and Related Risk Factors Among Overweight Premenopausal Women. Critics have criticized popular diets, especially those low in carbohydrates (i.e. Atkins) as well as those diets high in carbohydrates and low in fat (i.e. Ornish) to not be effective in sustained weight loss. So the debates go on and on and on.
The purpose of this study from Stanford was to compare 4 weight loss diets that represented a broad spectrum of low to high carbohydrate intake for weight loss and selected metabolic effects.
Three hundred eleven free-living, overweight/obese (body mass index (27-40), non diabetic, premenopausal women were recruited to participate in a 12-month randomized trial. All groups received weekly instruction for 2 months in their assigned diet (Atkins, Zone, Ornish, or LEARN) with an additional 10 month follow-up with weight and metabolic measurements and random phone calls to check on their adherence to the diets. The setting mimicked real life and the participants had to prepare their own meals.
The Atkins diet was the lowest in carbohydrates. The Zone diet focused on a 40-30-30 ratio of carbohydrate to protein and fat (a fairly low carb diet), The LEARN Diet (Lifestyle, Exercise, Attitudes, Relationships and Nutrition) follows dietary guidelines (USDA food pyramids), The Ornish diet is a high carbohydrate and extremely low fat diet.
The primary outcome measure at 12 months was weight loss. Secondary outcomes included lipid profile including LDL, HDL, non-high-density lipoprotein cholesterol, % body fat, waist-hip ratio, fasting insulin and glucose levels, and blood pressure. These measures were conducted at months 0, 2, 6, and 12.
What were the main findings?
At the end of the year, 77 women in the Atkins group had lost an average of 10.4 pounds; those in the LEARN group lost 5.7 pounds; the Ornish group lost 4.8 pounds and Zone women lost 3.5 pounds. In all four groups, however some participants lost up to 30 pounds. These women went down multiple dress sizes, but what about those who tried very hard and lost nothing and even worse even gained a few pounds? This is the most frustrating aspect to weight loss attempts.
After 12 months, women following the Atkins diet, relative to at least one of the other groups, had larger decreases in body mass index, triglycerides and blood pressure. Their high-density lipoproteins (good cholesterol) increased more than the women on the other diets.
The author offers some possible explanations as to why the Atkins diet may be more effective:
- The diet is very simple – get rid of all the refined carbohydrates in your diet such as white bread and pasta.
- People tend to drink more water with this diet decreasing their intake of sugar-sweetened beverages.
- The high protein content of this diet may be more satisfying than carbohydrates or fats which may have helped this group eat less without feeling hungry.
The author stated that about 1/3 of the women in the study qualified for the criteria of metabolic syndrome which suggests insulin resistance. This makes a low fat diet higher in carbohydrates less effective for people with this syndrome.
There is no single test for insulin resistance but people with metabolic syndrome are more susceptible. If you present three of the following, you may have some degree of insulin resistance:
WAIST SIZE: Women; more than 35 inch waist; Men; more that 40 inch waist
TRIGLYCERIDES: 150 or higher
HDL (good cholesterol): Women; under 50; men under 40
BLOOD PRESSURE: Systolic 130 or higher or Diastolic 85 or higher
BLOOD GLUCOSE: 110 or higher (fasting)
The authors conclude: While questions still remain about the long-term effects and mechanisms, a low-carbohydrate, high protein, high-fat diet may be considered a feasible recommendation for weight loss. Please discuss these findings along with your lab results with your doctor before embarking on any weight loss diet whether it is a low-fat or a low-carb diet. No one diet fits all!!