Trying to make sense of all the advice on fat in your diet can be difficult, especially when you have diabetes. On the one hand, certain fatty foods — especially fried foods — have been linked to poor health outcomes, including a higher risk of severe forms of heart disease. But there’s a growing recognition that fat in your diet isn’t all bad, especially moderate amounts of healthy fats from sources like nuts, seeds and avocados. And omega-3 fats from fish and other sources may have a protective effect against type 1 diabetes.
Still, there has been speculation that fat in your diet may play a role in weight gain in many people, increasing their risk of insulin resistance and type 2 diabetes. But a new analysis of studies suggests that broadly speaking, fat isn’t the enemy when it comes to a person’s type 2 diabetes risk.
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Fat from plants sources may be beneficial for diabetes risk
Of course, there are many different types of fat found in foods, which may have different effects on the risk of developing diabetes — something that researchers tried to figure out in a research review and analysis published in the journal PLOS Medicine. They looked at 23 studies — conducted in the United States, Europe, Asia and Australia — that examined the relationship between participants’ fat intake and whether they developed type 2 diabetes. These studies were included because they contained information on participants’ intake of animal fat, vegetable (plant) fat, total fat, and individual types of fat like saturated, monounsaturated and polyunsaturated fatty acids. (Omega-3 is a type of polyunsaturated fatty acid.)
Saturated fat can be found in animal sources like red meat, poultry and dairy products, as well as certain plant sources like palm oil and coconut oil. Monounsaturated and polyunsaturated fats are found in many different plant sources, including vegetable oils, nuts, seeds and avocados, while omega-3 fats are found in walnuts, flaxseed and fatty fish like salmon, herring and mackerel.
Overall, the researchers found only a weak relationship between participants’ intake of any types of fat and their risk of getting type 2 diabetes. And based on the design of the studies they looked at, the researchers concluded that their findings were “limited by very low to moderate certainty of evidence.” But despite these disclaimers, there were some important findings in the analysis.
There was no relationship between total fat intake and the risk of developing type 2 diabetes. But there was a protective effect observed from eating more vegetable fat, especially at lower levels up to 13 grams per day compared with a lower intake of these fats. There was also an apparent protective effect from eating more saturated fat, at levels above 17 grams per day. Weaker protective effects were seen from eating more polyunsaturated fats, up to about 5 grams per day, and a type of omega-3 fat called alpha-linolenic acid (ALA) up to about 560 milligrams per day.
The researchers cautioned that the strength of their findings were limited by an unexplained high level of inconsistency among the 23 studies, as well as the fact that the intake of different fats was estimated on a broad food-group level in the studies. It’s possible, then, that there were widespread errors in how fat intake was estimated.
Are current guidelines on fat helpful?
The researchers noted that under dietary guidelines on preventing diabetes in most countries, including the United States, people are urged to limit their intake of total fat and animal fat, and to focus on getting fat from plant sources. In addition, these guidelines state that people should limit their intake of saturated fat and instead get enough monounsaturated, polyunsaturated and especially omega-3 fatty acids.
But if the findings in this study are accurate, there is no basis for recommending that people limit their intake of saturated fat to reduce their diabetes risk. There’s also only a limited basis for recommending that people limit their intake of animal fat, or to increase their intake of omega-3 fats above the fairly low level of 560 milligrams per day of ALA — about half the amount currently recommended for women, 1.1 grams, and less than half of the 1.6 grams recommended for men, according to the National Institutes of Health.
Of course, there may be other health benefits from limiting your intake of animal fat and saturated fat, beyond their effects on developing diabetes. But at least according to the available evidence in this analysis, there’s little to no basis for recommending limiting these types of fat — or the total fat in your diet — to reduce your risk of type 2 diabetes.