Dietary fats provide energy and support vital bodily functions, but as we learned previously, excess fat from food can create ‘gum in the lock’, making it harder for insulin to do its job—a process known as insulin resistance.

It’s also important to note that not all dietary fats are created equal. Saturated and trans fats can promote insulin resistance and increase the risk of heart disease, whereas unsaturated fats tend to have neutral or beneficial effects—especially when they replace saturated and trans fats in the diet.

Let’s take a closer look at the different types of fat and which foods they’re found in.

Saturated fats

Saturated fats are found in foods such as butter, cheese, red meat, and palm and coconut oils.

They raise LDL cholesterol, which increases your risk of developing heart disease. They can also interfere with how insulin signals cells to take up glucose and may promote inflammation.

Higher intakes of saturated fat are associated with reduced insulin sensitivity, so they should be limited and replaced with unsaturated fats where possible.

Trans fats

Trans fats are present in many processed foods, some margarines, and fried items.

They raise LDL cholesterol, lower HDL cholesterol, and strongly promote insulin resistance through lipid build-up and inflammation.

Trans fats are best avoided entirely, as they substantially increase cardiovascular risk and are strongly linked with insulin resistance and type 2 diabetes.

Monounsaturated fats

Monounsaturated fats are found in foods such as olive oil, avocados, and nuts like almonds.

They can lower LDL cholesterol while maintaining HDL levels, and improve insulin sensitivity—particularly when they replace saturated fats in the diet.

Polyunsaturated fats

Polyunsaturated fats are present in walnuts, sunflower oil, seeds, and other plant foods.

They include essential omega-3 and omega-6 fats, which support insulin function and reduce inflammation, particularly when replacing saturated fats. Overall, they are protective against heart disease and can help counter insulin resistance when used in place of saturated fats.

Reversing insulin resistance

Diets high in saturated and trans fats contribute to the development and maintenance of insulin resistance. The goal is therefore to reduce, or ideally eliminate, these fats from the diet.

Even small dietary shifts can make a meaningful difference. In large prospective US cohorts, replacing just 5% of total energy from animal protein—often accompanied by saturated fat—with plant protein was associated with approximately 23% lower risk of type 2 diabetes.

So the more you fill your plate with fruits, vegetables, legumes, and other whole plant foods, the more you can reduce your risk—or improve blood glucose management if you’re already living with diabetes.