Sugar often gets all the blame for causing high blood sugar, but saturated fats cause insulin resistance and block the action of insulin. So what is the connection between saturated fats and insulin resistance?
Insulin is required to transport glucose out of the bloodstream and inside the cell. The ability of insulin to transport glucose inside the cells is crucial for lowering blood sugar.
Insulin resistance is a state where the cells become resistant to the action of insulin thus, glucose cannot get inside the cell, which causes high blood sugar.
Eating a diet high in saturated fats causes insulin resistance which results in impaired glucose tolerance. The sugar gets all the blame as that is what is measured daily in diabetes. Behind the scenes, what isn’t measured daily is the level of free fatty acids in the blood and insulin levels.
The muscles uptake glucose from the bloodstream and store glucose for energy production in muscle tissue. The elevation of fat levels in the blood causes insulin resistance by inhibiting the transport of glucose into muscle tissue.
This study demonstrates a 50 % reduction in the rate of glucose transport and storage in the muscle tissue. The increased insulin resistance caused by fats decreases the uptake of glucose from the bloodstream into the muscles. As a result, blood sugar levels elevate after eating fats.
As fats are cleaned out of the bloodstream, insulin sensitivity increases, blood sugar levels improve. Glucose tolerance is improved when excess fats are not in the bloodstream.
The consumption of fat delays stomach emptying that causes a late rise in blood glucose. The effect of a high-fat meal on insulin resistance can last 5-10 hours after the meal affecting blood sugar levels following additional meals.
For example, you may eat a high-fat breakfast with scrambled eggs, cheese, sausage, and avocado and get a low blood sugar reading 2 hours post this high-fat meal due to minimal conversion of carbohydrates into glucose.
Yet for lunch, you may decide to have a high carbohydrate meal such as a vegetable sandwich with a slice of cheese on bread with a piece of fruit and note a high blood sugar reading 2 hours post this meal. Many people would look at this and remark see, the sugar and carbs caused my blood sugar to elevate like crazy. I can’t eat carbs.
But the cause for the elevation in the blood sugar post-lunch was the increased insulin resistance caused by the high-fat breakfast.
The elevated free fatty acids in the bloodstream from the breakfast have caused insulin resistance inhibiting the ability of insulin to transport glucose out of the bloodstream and inside the cell.
Fats and insulin resistance
Another study provides strong evidence that free fatty acids impair insulin sensitivity and increase the need for insulin in type 1 diabetes. Two meals eaten by type 1 diabetics had equal carb and protein content but varied fat content.
One meal had 10 grams of fat, and the other meal had 60 grams of fat. The high-fat meal required more insulin than the low-fat meal. Higher blood sugar numbers were still noted in the group fed the high-fat meal despite the additional insulin. These findings prove that dietary fat increases blood glucose levels after a meal and increases the need for more insulin to lower blood sugar after eating.
Fat doesn’t affect everyone’s blood sugar the same as some people have more tolerance to the blood glucose altering effects of fat. The best way to find out how fats affect your blood sugar is to test.
During my diagnosis of gestational diabetes, I noted that eating higher fat meals raised my blood sugar levels the most. I got my highest blood sugar readings out of the target range post meals that contained a higher fat content combined with carbohydrates.
In particular, the processed oils in fries or saturated fats in combo with refined carbohydrates such as rice crackers and bread caused my highest blood sugar readings after meals.
The combination of processed carbohydrates and fats is everywhere, such as in ice cream, chips, pastries, baked goods, pizza, etc.
Insulin resistance and fatty liver
A fatty liver increases the risk of type 2 diabetes and insulin resistance.
This study demonstrates the harmful effects of saturated fats in increasing intrahepatic triglyceride content (fatty liver) and insulin resistance.
Thirty-eight overweight people were overfed 1000 extra calories per day of either saturated fat, unsaturated fat, or simple sugars for three weeks.
The overfeeding of saturated fat significantly increased fatty liver more than unsaturated fat or simple sugars. The saturated fats also induced insulin resistance.
When it comes to fats and insulin resistance, the type of fat consumed needs to be considered as saturated fats increase insulin resistance more than unsaturated fats.
Processed saturated fats such as coconut oil are more calorie-dense and nutrient deficient than nuts and seeds in their whole food form.
Adipose tissue can safely store excess fat, but the liver cannot. The build-up of fatty deposits in the liver, also known as non-alcoholic fatty liver disease, is the first adverse metabolic consequence of insulin resistance. Ninety percent of obese type 2 diabetes have non-alcoholic fatty liver disease.
Insulin resistance that develops in the liver is related only to the fatty acid levels in the liver and not the level of visceral fat or adipose fat. Insulin resistance that develops in the liver first is why some people with a normal BMI can have elevated blood sugar even though they are not overweight.
Some people are “metabolically healthy obese” as they have excess body fat as adipose tissue. Fat cells in adipose tissue are the only cells in the body designed to safely store large amounts of fat.
It is the build-up of fat in the liver and muscle that is more problematic, leading to insulin resistance. Yet over time, even overloaded adipose tissue can become insulin resistant.
Insulin resistance is often characterized by increased inflammation. Saturated fats contain high amounts of pro-inflammatory arachidonic acid however unsaturated omega-3 fatty acids are anti-inflammatory. The anti-inflammatory properties of omega-three fats are one reason why fish oil is beneficial for weight loss, and saturated fats are not.
The kanwu study on humans done on healthy individuals demonstrated that saturated fats increased insulin resistance. Decreasing saturated fatty acids and increasing monounsaturated fatty acids improve insulin sensitivity but have no effect on insulin secretion.
To reverse insulin resistance these studies indicate that it is best to reduce the amounts of fats in your diet, especially saturated fats. This is in line with the number one dietary recommendation in the Mastering Diabetes book and coaching programs.
Substituting saturated fats with unsaturated fatty acids can improve insulin sensitivity as the type of fat content matters.
My experience with saturated fats and insulin resistance during gestational diabetes.
During my diagnosis with gestational diabetes, I noticed that high-fat meals, particularly processed oils or saturated fats caused my blood sugar to elevate the most after eating. I also got higher fasting blood sugar levels in the morning following a dinner higher in fat content.
When I look at my strategene genetic report, I can see how I am prone to insulin resistance as I have SNPs in the APOE gene, which is involved in fat transportation.
I also have SNPs in the methylation pathway and PEMT gene, which makes me more prone to fats building up in the liver. A fatty liver then leads to insulin resistance.
I upregulate saturated fats into arachidonic acid, which are pro-inflammatory. Additionally, I have a reduced ability to convert plant-based omega-3 fats into DHA, which are anti-inflammatory.
Knowing this information while tracking my blood sugar helped me manage and reverse my gestational diabetes through diet. I focused on eating plant-based whole foods to reverse insulin resistance and reduced my overall fat intake, including saturated fats.