Two daily servings of fermented dairy, full-fat or low-fat, did not change insulin sensitivity in a 12-week trial

Eating two servings a day of fermented dairy foods for 12 weeks, in place of nondairy foods, did not improve insulin sensitivity in adults at higher cardiometabolic risk, whether the dairy was full-fat or low-fat, according to a randomized trial published online on 14 August 2026 in Current Developments in Nutrition. The one statistically significant result was in waist circumference: it fell by 1.62% with full-fat fermented dairy and rose by 2.21% with the control foods, an estimated difference of 4.13% (p = 0.047).

What the researchers did

Teams at Midwest Biomedical Research, Indiana University and the Illinois Institute of Technology enrolled adults with a BMI of 25.0 to 39.9 and fasting triglycerides of at least 120 mg/dL. Participants were randomly assigned to one of three groups for 12 weeks: 2 servings a day of full-fat fermented dairy foods, 2 servings a day of low-fat fermented dairy foods, or 2 servings a day of nondairy control foods. The study foods were provided. The analysis included 110 people with an average age of 45.7 years and an average BMI of 31.3.

The main outcome was the Matsuda index, a measure of how well the body responds to insulin. The researchers also tracked blood lipids, inflammation markers, body measurements and blood pressure. None of these differed between groups except waist size in the full-fat group.

How strong is the evidence?

Moderate for a neutral result. Random assignment and provided foods are strengths. But 110 people split across three groups is a small trial, it lasted 12 weeks, and it measured risk markers rather than heart disease or diabetes. The waist finding was just under the usual significance threshold and was not the main outcome, so it should be read with caution. The lead author reports research grants and advisory roles with several food organizations, including the National Dairy Council.

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