A Canadian randomized trial has found that including three daily servings of full-fat dairy in the diets of adults with overweight or obesity does not negatively impact body weight, blood markers, or metabolic health over a 12-week period. The study was published in The Journal of Nutrition.
Researchers conducted the trial at two Canadian universities, enrolling 74 healthy adults aged 25 to 60 years who were classified as overweight or obese. Participants were randomly assigned to one of three groups: a low-dairy, energy-restricted diet; an energy-neutral diet with three servings of full-fat dairy per day; and an ad libitum diet (no calorie restriction) also including three servings of full-fat dairy. All participants received dietary counselling based on Canada’s Food Guide (CFG).
According to the study authors, "Compared with diets low in dairy, daily consumption of full-fat dairy for 12 weeks did not negatively affect blood glucose, blood lipids, body composition, or weight. It improved calcium and protein intake without conferring measurable cardiometabolic benefit or harm."
Measurements taken throughout the intervention included anthropometric data, resting metabolic rate, blood pressure, fasting blood markers, urine samples, and detailed dietary intake records. At baseline and during the study period, all groups showed similar improvements in adherence to CFG recommendations such as increased whole-grain intake and reduced processed food consumption.
Body weight and BMI decreased modestly only in the energy-restricted low-dairy group but remained stable in both groups consuming full-fat dairy. There were no significant changes across any group regarding waist circumference, body fat percentage, fat-free mass, or resting metabolic rate.
Systolic blood pressure fell in both the ad libitum dairy group and the energy-restricted group. Hip circumference declined slightly only among those on the ad libitum diet. Blood lipid levels—including cholesterol—and measures like glucose and glycated hemoglobin remained unchanged by dairy intake during the study.
Nutrient analysis revealed that those consuming more full-fat dairy had higher intakes of calcium and protein than those on a low-dairy diet; calcium levels exceeded recommended amounts only in these groups.
The researchers noted: "These findings demonstrate that consuming three daily servings of full-fat dairy for approximately three months does not negatively affect body weight, cardiometabolic markers, or metabolic health in metabolically healthy adults with overweight or obesity when combined with dietary guidance from the CFG."
They further stated: "The results support the view that full-fat dairy can be incorporated into a healthy dietary pattern while improving intake of limiting nutrients such as calcium and protein without evidence of short-term cardiometabolic harm." However, they emphasized that these findings should be interpreted as showing dietary compatibility rather than providing evidence for cardiometabolic benefit.
The trial's limitations include its relatively small sample size—affected by disruptions related to COVID-19—and short duration. Most participants were metabolically healthy at baseline; therefore results may not apply to individuals with existing metabolic disease or over longer periods.
Researchers concluded that adding full-fat dairy to diets guided by national recommendations does not pose adverse effects for adults who are overweight or obese but suggested further research is needed involving broader populations over longer durations.
