Fats and Insulin Resistance March 10, 2009
Posted by Dr Dan in fat, insulin, saturated fat.trackback
Here is an article I wrote for the paleo diet newsletter and if you want to subscribe go to thepaleodiet.com.
Insulin resistance is thought to be an important contributing factor to the modern diseases of civilization such as metabolic syndrome, blood lipid disorders, hypertension, obesity and type II diabetes. Although genetics plays a role in insulin resistance the observation that obesity and diabetes are increasing at alarming rates worldwide suggests that there are vital environmental factors that need to also be considered.
Although carbohydrates play an integral role in insulin resistance by elevating glucose levels there is also strong evidence that the amount and quality of free fatty acids consumed also contributes to insulin sensitivity. It has been shown in rats that under certain circumstances free fatty acids are required for glucose-stimulated insulin resistance. Essentially, when rats are infused with a high level of glucose, in the absence of fatty acids, the insulin response is non-existent. In contrast, when this occurs in the presence of high levels of free fatty acids glucose-stimulated insulin resistance is extremely elevated. It was shown in these studies on rats that the amount of saturation of the fatty acid was also correlated with insulin secretion. The more saturated the fat the higher the insulin burst. Thus, in rats it seems that free fatty acids are vital to produce glucose-stimulated insulin resistance and of these saturated fats have the most detrimental effects.
Whether this occurs in humans was investigated by Vessby et al. (2001), who established that the amount and quality of fat in the diet could also be important for the development of insulin resistance in our species. A group of 162 healthy subjects were given an isocaloric diet high in either saturated or monounsaturated fat for three months. As in the rats, insulin resistance depended on the amount of fatty acids consumed and the saturation of those fatty acids. When the amount of energy gained from fat was > 37% it was found that insulin sensitivity was impaired in both the saturated fat group (-7.8%) and the monounsaturated fat group (-3.3%). However, when the amount of energy coming from fat was < 37% a significant difference was found with saturated fat still decreasing insulin sensitivity (-12.5%) but monounsaturated fat increasing it (+8.8%). Therefore, within the context of this study, it would seem that insulin resistance can be improved on a diet consisting of less than 37% of energy from fat, and this fat coming predominantly from monounsaturated fatty acids.
Its important to note that I am not against saturated fats as everyone knows. But maybe they are best if they can be balanced out with monounsaturated fats over a week to counteract these effects. Of course since hunter gatherers probably didn’t have diets high in carbs anyway there would be nothing for the saturated fats to work on. It looks like there is a bad synergy between carbs and saturated fats and maybe there is something in that!!
References
DeFronzo RA, Ferrannini E (1991) Insulin resistance: a multifaceted syndrome responsible for NIDDM, obesity, hypertension, dyslipidemia and atherosclerotic cardiovascular disease. Diabetes Care 14: 173-194
Seidell JS (2000) Obesity, insulin resistance and diabetes – a world wide epidemic? British Journal of Nutrition 83 (Suppl 1): S5-S8.
Evans JL, Goldfine ID, Maddux BA, Grodsky GM (2003) Are oxidative stress-activated signaling pathways mediators of insulin resistance and beta-cell dysfunction? Diabetes: 52(1): 1-8
Stein DT, Esser V, Stevenson B, Lane KE, Whiteside JH, Daniels MB, Chen S & McGarry JD (1996) Essentiality of circulating fatty acids for glucose-stimulated insulin secretion in the fasted rat. Journal of Clincal Investigation 97: 2728-2735.
Stein DT, Stevenson BE, Chester MW, Basit M, Daniels MB, Turley SD & McGarry JD (1997) The insulinotropic potency of fatty acids is influenced profoundly by their chain length and degree of saturation. Journal of Clinical Investigation 100 (2): 398-403
Vessby B, Uusitupa M, Hermansen, K, Riccardi G, Rivellese A, Tapsell LC, Nalsen C, Berglund L, Louheranta A, Rasmussen BM, Calvert GD, Maffetone A, Pedersen E, Gustafsson IB & Storlien LH (2001) Substituting dietary saturated for monounsaturated fat impairs insulin sensitivity in healthy men and women: the KANWU study. Diabetologia 44: 312-319
Another way to look at this might be to point out that if consuming a diet high in fat it is extremely important to keep insulin resistance down by moderating sugar and carbohydtrate intake. This may be why the high fat/ low carb diet works. In a typical western diet of high fat/high carbohydrate… this sounds like a recipe for disaster.
The SoG
Thanks for publishing this.
The 2001 human study by Vessby et al is very helpful to me since I deal with humans. The monounsaturated fats in that study were predominantly from high-oleic sunflower oil. Olive oil was negligible by design. The study authors don’t discuss whether the observed metabolic changes apply only to sunflower oil or not. The implication is that all sources of monounsaturated fats would have the same effects – which may or may not be true. (I haven’t tried to find out.)
Lp(a) [lipoprotein(a)] rose by 12% in the monounsaturated fat diet, compared to the unsaturated fat diet (no change). Lp(a) is a risk factor for atherosclerotic complications.
So maybe you shouldn’t fee too bad about your high saturated fat intake.
I’ll be looking for similar studies in people with metabolic syndrome, prediabetes, and diabetes..
-Steve
The Vessby study food was supplied by several food manufacturers, with additional support from the International Council of Olive Oil and others. Nothing necessarily wrong with that.
SoG – yes thats what I thought too!!! I might amend it because I think thats important.
Steve – your right it is a bit of a leap to say sunflower oil works and therefore this must be true for monounsaturated fats. Then again its kind of backed up by the animal studies and shows the same thing so it does have some credibility. Also to clarify Lp(a) rose in monounsturated vs unsaturated? By unsaturated did you mean polyunsaturated or did you mean saturated.
Referring to Vessby’s article of 2001, I wrote above that:
“Lp(a) [lipoprotein(a)] rose by 12% in the monounsaturated fat diet, compared to the unsaturated fat diet (no change). Lp(a) is a risk factor for atherosclerotic complications.”
I meant to write, “Lp(a) rose by 12% in the monounsaturated fat diet, compared to the SATURATED fat diet (no change).”
Vessby’s saturated fat diet was described as including butter and a table margarine containing a relatively high proportion of saturated fatty acids. In contrast, the monounsaturated fat diet used a spread and margarine containing high proportions of oleic acid derived from high-oleic sunflower oil.
You know, but your readers may not, that the main monounsaturated fat in olive oil is oleic acid.
I’m sorry to obfuscate an inherently confusing topic!
-Steve
I thought you mean’t saturated fats. Thanks for the info.
[...] I might also watch the saturated fat intake too since this has also been associated with increased insulin resistance. I know that this is a controversial comment but at the moment Im not taking any risks. Also, Im [...]