This post is written by Osama Hamdy, M.D., Medical Director, Obesity Clinical Program, Director of Inpatient Diabetes Management at Joslin Diabetes Center, Assistant Professor of Medicine at Harvard Medical School. Dr. Hamdy is also the Director of the Why WAIT program where he works with people to improve their diabetes management through weight loss. Dr. Hamdy is also the author of the Diabetes Breakthrough.
In 1977, the Select Committee On Nutrition and Human Needs of the US Senate recommended that people increase their carbohydrate intake to 55 to 60 percent of the total caloric intake, while reducing fat consumption from approximately 40 percent to 30 percent of the total daily calories. The aims of these recommendations were to reduce health care costs and maximize the quality of life of Americans, as stated by George McGovern, the chairman of that committee.
The proposed cost saving was predicted to result from the possible reduction in the incidence of heart disease, cancer and stoke, as well as other killer diseases. Despite controversy that the recommendations were based on weak scientific evidence, the United States Department of Agriculture (USDA) created in 1980 a food pyramid representing the optimal number of servings to be eaten each day from each of the basic food groups. Carbohydrates were placed at the base of the pyramid (making up the largest portion of caloric intake, 6 to 11 servings per day), and fats were placed at the tip of the pyramid to show that they should be “used sparingly.”
Unfortunately, the results of these recommendations turned out to be the opposite of what the USDA expected.
What has been aptly described as a “national nutritional experiment” contributed, as we know now, to the increased prevalence of obesity. And, contrary to the main aims of the recommendations, the prevalence of type 2 diabetes — and cardiovascular disease — went up significantly.
Why did this happen? Physiologically, an increase in carbohydrate intake results in an increased insulin response to carbohydrates, which through its fat-storage promoting action increases obesity. And, it has been shown, that accumulation of fat inside the belly (visceral fat) is associated with chronic inflammation that is directly related to type 2 diabetes and heart attacks.
The problem is equally bad for people who already have type 2 diabetes. We know today that increasing the carbohydrate load in the diabetes diet increases what is called glucose toxicity and consequently increases insulin resistance, triglycerides level and reduces beneficial HDL-cholesterol.
At the turn of the twentieth century (way before the USDA recommendations represented by the food pyramid) what we now know as type 2 diabetes was predominantly defined as a carbohydrate intolerance disease and was mainly treated by reducing carbohydrates intake. Carbohydrates restriction was particularly successful in treating diabetes before the discovery of insulin. Drs. Elliot P. Joslin and Fredrick Allen, the fathers of diabetes science, successfully treated their patients diagnosed with fatty diabetes (later known as type 2 diabetes) with a diet very low in carbohydrates. Today, Elliott Joslin’s diet would be considered eccentric, as seen by the reaction in the medical community to its reincarnation as the Atkins Diet.
Such extreme reduction of carbohydrates, despite being very successful in treating type 2 diabetes before insulin discovery, was in fact shown to be associated with some uncomfortable side effects, like constipation, headache, bad breath and muscle cramps. But, although the recommended amount of carbohydrates intake was significantly relaxed after the discovery of insulin in 1922, it never exceeded 40% of the daily caloric intake, an amount that was shown to reduce blood glucose and triglycerides. Thus, it was absurd that when the USDA recommendations were published several medical societies recommended increasing carbohydrates and decreasing fat intake for patients with diabetes.
Since 2003, many clinical trials have confirmed that reducing carbohydrates is still superior to reducing fat in decreasing body weight and improving glucose control. It has also been shown that reducing carbohydrates for patients with type 2 diabetes improves their sensitivity to their own insulin; reduces belly fat and triglycerides; and increases good cholesterol (HDL-cholesterol).
Recently an analysis of several studies (meta-analysis) showed that reducing carbohydrates load (amount) and glycemic index (the effect of particular carbohydrates-containing food on blood glucose) was associated with reduced risk of developing type 2 diabetes. After weight reduction, maintaining a diet that lowers the consumption of high glycemic-index foods and is higher in protein was shown to better maintain weight loss for longer duration than any other dietary composition.
The Joslin Guidelines
Since 2005, the Joslin Clinic has been recommending a reduction of carbohydrate intake to 40-45% of the total daily calories and avoidance of food that rank high on the glycemic index of carbohydrates (see glycemic index table). Joslin’s 2005 guidelines for overweight and obese patients with type 2 diabetes or those at risk to develop type 2 diabetes, which were revised in 2011, continue to recommend reducing carbohydrates intake to prevent and treat patients with type 2 diabetes and weight problems.
Recently, most medical societies departed from the recommendation of high carbohydrates intake and recommended individualization of the nutrition needs. At Joslin we have clinical proof that this is the right decision. Since 2005 we have been following the Joslin Guidelines in our weight management program (Why WAIT). The 44 groups of type 2 patients who have gone through the Why WAIT program and follow the Joslin Guidelines have lost a total of 10,000 lbs., have improved their diabetes control and cut their medications significantly.
Unfortunately, many healthcare providers and dietitians across the nation still recommend high carbohydrate intake for patients with diabetes, a recommendation that may harm their patients and contribute to increasing obesity and worsen diabetes control and consequently increase the chance of developing diabetes complications.
It is now clear that a major mistake was made in the 1970’s in recommending an increase in carbohydrates to >40% of the total daily calories. This era should come to an end if we seriously want to reduce obesity and type 2 diabetes epidemics.
To learn more about the Why WAIT program click here.
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