Low-Carb Diets Linked With Type 2 Diabetes

By Tim Harlan, M.D.
Updated Jun 24, 2011

Fad diets are clearly not all they are cracked up to be. Most are simply made up of theories that seldom get put to the test other than with the anecdotal evidence of users who swear by them. When put to the test of time, however, they fail those who use them and when carefully scrutinized by scientists and researchers they collapse under the weight of the evidence.

Low-Carb diets are the prototype for this. They’ve been around for well over 100 years in one form or another, with the most popular version being marketed by Dr. Atkins over the last 40 years. People do lose weight, but not for the reasons put forth by those who champion such plans. The weight loss comes partly from eating fewer calories and partly because in this day and age, eliminating carbohydrates means eliminating calorie dense, highly processed foods (most of which contain high fructose corn syrup (HFCS)).

I can’t imagine why anyone would follow a diet — any diet — that takes entire food groups away from you. There’s no reason to give up great foods like pasta, potatoes, beans and corn to lose weight or to be healthier. Giving up these foods is one of the main reasons that the Atkins diet is not a diet that can be sustained for the long term. Further, such diets seldom prepare people for eating real food: when they go off the diet they usually gain the weight back, and then some.

There’s been concern for years about the long term health risks of such diets. We’ve seen that those eating higher protein diets that are also high in saturated fat were more likely to develop heart disease than those whose higher protein diet came from vegetable protein sources. Interestingly, those women eating a strict low-carbohydrate diet weighed more than those eating a more normal diet.(1) Their Body Mass Index was higher in all categories. We also know that extremely-low-carbohydrate diets also seem to affect one’s cognitive abilities.(2)

Recently a group of researchers affiliated with Harvard University looked at whether low carbohydrate diets such as the Atkins diet had any effect on a person’s risk of developing Type 2 diabetes.(3) They made use of information gathered through the Health Professionals Follow-Up Study, which included over 40,000 men who did not have Type 1 or Type 2 diabetes, heart disease or cancer at the start of the study, which began in 1986. Every other year the participants responded to a health and lifestyle survey, along with a food frequency questionnaire which allowed the researchers to assess the subjects’ usual diets.

After 20 years of follow-up (ending in late 2006), the researchers looked at the participants’ dietary information and identified those persons whose diets would be considered “low-carbohydrate diets.” Those persons’ diets were then further broken out into three different varieties of low-carbohydrate diets based on a “low-carbohydrate diet score” that ranged from zero (higher carbs, lower protein and fats) to 30 (lower carbs, higher proteins and fats):

Low-carbohydrate, high total protein and high total fat

Low-carbohydrate, high animal protein and high animal fat

Low-carbohydrate, high vegetable protein and high vegetable fat

The researchers then compared the diets of those who developed Type 2 diabetes with those who did not. They found that those following diets high in animal protein that included red and processed meats and a high percentage of animal fat (as opposed to fats from vegetable sources) were almost 75 percent more likely to develop Type 2 diabetes than those who followed a more moderate diet. The risk was highest in those men who were also obese.

There was a little bit of good news in this study. Those who ate a diet that was low in carbohydrates but high in vegetable proteins and fats were not found to have a higher risk of Type 2 diabetes. That combination appeared to be protective for those men under the age of 65, but that effect was lost in those who were older. That group also weighed less than their low-carb/high animal protein counterparts. Not a lot less, mind you, with the difference only being a body mass index of 25.5 (high vegetable protein and fat group) versus 26.3 (high animal protein and fat group).

The one thing to understand about this study is that it is not interventional research. The participants weren’t necessarily on the Atkins diet and we don’t know how many might have been attempting to lose weight during the study. The data reported were simply drawn from what the participants were eating during the study. We don’t know if some of them lost or gained weight or were on and off of diets. The results simply show that consuming less animal protein and fat is a better, healthier choice.

One interesting observation that the researchers don’t comment on is that the lower the low-carbohydrate diet score (i.e., those eating the most carbohydrates), the lower the risk of diabetes. This applies to both groups, whether they ate a high animal protein and fat or a high vegetable protein and fat diet. Moderate carbohydrate consumption with most of the protein and fats coming from vegetable sources appears to be the best choice.

As an aside, the study also reported that a fair number of the physicians smoked. Fourteen percent of those whose diets were most like the prototypical Atkins style diet, consuming low-carbs with high intake of animal protein and fat, also smoked.

Research about diet has come a long way in the last 20 years. It’s clear that the dialogue should not be about macronutrients. The challenge is as follows: For researchers there’s certainly a reason to focus on the composition of food to understand what works best. But for day to day life the focus should be on food. It’s clear that eliminating whole groups of foods doesn’t work and does more harm than good.

We already know that the Mediterranean Diet is the best diet for those who have Type 2 diabetes4 and that following such a diet reduces your risk of developing heart disease as well as diabetes. There’s no need to give up carbohydrates in order to reduce your risk of diabetes when you can eat real, delicious food and still reduce your risk of diabetes.