Saturated fat is typically found in fatty animal products such as butter, cheese and red meat. It is generally considered unhealthy and is linked to high levels of cholesterol, as well as type 2 diabetes.
Different types of saturated fat can be spotted in the body by looking for chain-like saturated fatty acid molecules which contain either an odd or even number of carbon atoms.
Molecules with odd numbers of carbon atoms - 15 and 17 - which are associated with eating dairy products such as yoghurt, cheese or milk, appeared to have a protective effect. Those with an even number - 14, 16 and 18 - were associated with a higher risk of type 2 diabetes.
Dr Forouhi added: "These odd-chain saturated fatty acids are well-established markers of eating dairy fats, which is consistent with several recent studies, including our own, that have indicated a protective effect against type 2 diabetes from eating yoghurt and other dairy products."
The findings appear in the journal The Lancet Diabetes and Endocrinology.