Continuing my series in which I evaluate the validity of various anti-meat arguments, we look next to diabetes. It has been suggested that meat, especially red meat, might contribute to diabetes by worsening insulin resistance, which prevents the body from clearing glucose from the blood stream. Since there isn’t a widely agreed upon mechanism for how meat might do this, let’s look at it from different possible angles.
Generally speaking, one of the most powerful influences on insulin resistance and diabesity is the amount of body fat a person has. Putting on fat increases insulin resistance (1,2,3,4) and losing fat decreases insulin resistance (2,4,5,6). Thus, certain foods or substances, like caffeine and ephedrine, can improve insulin sensitivity when they aid in weight loss (7), but can actually worsen insulin sensitivity in the absence of a change in weight (8,9,10).
Meat is fairly satiating (13,15) and diets high in protein from meat have frequently been shown to be good at producing weight loss (11,12), so I looked for studies in which weight changes were the same between groups.
One study examined the effects of weight loss in two groups, one eating more protein from meat and dairy products and the other eating more carbohydrates (14). Fat intake was essentially the same between groups and there was no difference in the amount of weight lost during the trial. Ultimately there was no differences between groups on various measures of insulin resistance.
A study similar to the previous one was performed on type 2 diabetics (16). Once again, the group eating more protein (largely from meat) did not end up with worse insulin sensitivity than the group eating more carbohydrates.
Another study formed several groups, including a high carbohydrate, high fiber group and a high protein group (17). The higher carbohydrates group was told to eat foods like brown rice, fruit, legumes, potatoes, vegetables, and whole grains while the high protein group was told to eat legumes, low fat dairy products, low fat meat, and vegetables. At 6 weeks into the trial the higher carbohydrate group had better insulin sensitivity than the high protein group, but by 18 weeks there was no statistically significant difference between the two groups. Worth noting about the difference seen at 6 weeks is that low fat dairy products have been shown in some studies to produce greater insulin resistance compared to meat (18), so the midpoint difference may have been mediated by dairy consumption.
Finally, one study comparing a meat rich diet to a diet rich in low glycemic index carbohydrates found no difference in markers of insulin sensitivity in type 2 diabetics (22).
So while it seems meat protein doesn’t increase risk of diabetes, what about the fat? Well, in a previous post I pointed out that saturated fat is not worse for insulin sensitivity than monounsaturated fat (since I wrote that post I found more studies supporting this-see references 19, 20, 21). In addition, I also also cited evidence that n6 polyunsaturated fat is worse for insulin sensitivity than monounsaturated fat, suggesting it is thus worse than saturated fat.
So meat fat likely doesn’t adversely affect insulin resistance compared to other types of fat, what about compared to carbohydrates? Several studies have found that saturated fat does not worsen insulin sensitivity compared to carbohydrates, even low glycemic, complex carbohydrates (20,21,22). Furthermore, diets high in monounsaturated fat (the most common fat in meat) have also been shown to either not differ from or improve indices of glycemic impairment in numerous studies on individuals with poor insulin sensitivity (20,23).
The Method of Cooking
There is some preliminary evidence that high heat cooking of meat, perhaps via the formation of advanced glycation endproducts (AGE’s), may increase insulin resistance (24,25,26). Still, because the research on this issue did not examine the effects of high heat cooking meat alone, but the high heat cooking on several different foods, we can’t say the meat was causing negative effects. Still, further research may reveal that high heat prepared meat increases insulin resistance, but at this point such evidence is in its infancy. Either way, this would not apply to meat prepared using gentle methods of cooking.
From this it appears that eating meat does not promote insulin resistance or increase the risk of diabetes, unless perhaps the meat is cooked at very hot temperatures.