Rethinking dairy: Whole milk tied to healthier weight profiles

New research reveals how whole milk could defy the odds by promoting healthier weight profiles and reducing obesity prevalence in U.S. adults.

In a recent cohort study published in the journal Nutrition Research, researchers in the United States of America (US) investigated the relationship between whole milk intake and body weight in adults. They found that whole milk intake was inversely linked to weight, body mass index (BMI), waist circumference, and obesity prevalence and positively associated with the desire to lose weight and, in some cases, the desire to gain weight.

Background

Global Obesity Surge: The prevalence of obesity has nearly tripled since 1975, highlighting a significant global health challenge.

Obesity is a global health challenge affecting over 1 billion people and is linked to serious diseases like cardiovascular conditions, diabetes, and cancers. In the US, over 42% of adults are obese, contributing to significant health and economic burdens.

Obesity arises from complex interactions of genetic, socioeconomic, lifestyle, and dietary factors. Healthy diets and active lifestyles are key to weight management, with milk and dairy products consistently recommended for their rich nutrient content.

Evidence suggests that dairy consumption, regardless of fat content, is linked to neutral or reduced obesity risk, though clinical trials without calorie restriction often show no significant effects.

Traditional dietary guidelines favor low-fat dairy to reduce obesity risk, but emerging research indicates whole milk may not increase weight gain and could even lower obesity risk, warranting further studies on long-term effects and behaviors.

Whole milk may contribute to these benefits through mechanisms such as promoting satiety, delaying gastric emptying, and replacing calorie-dense sugary beverages.

Therefore, researchers in the present study examined whether whole milk intake is associated with body weight and related measures in US adults and if milk intake early in life affects body weight later in life.

About the study

Data of US adults aged 20 years and above were obtained from nine cycles of the National Health and Nutrition Examination Survey (NHANES, 2001–2018). NHANES, a nationally representative dietary survey, collects health, nutrition, and demographic data through interviews and physical examinations, following rigorous ethical protocols. The data were publicly available, ensuring transparency and reproducibility of the study.

Regional Disparities: Obesity rates vary by region, with the Americas reporting a 67% prevalence of overweight adults, compared to 31% in the South-East Asia and African regions.

The sample included 43,038 adults after excluding participants with incomplete dietary records or pregnancy/lactation. Whole milk intake was assessed using 24-hour dietary recalls and categorized into plain and flavored whole milk. Milk intake history was evaluated for three life stages (ages 5–12 years, 13–17 years, and 18–35 years) using self-reported data obtained via questionnaires.

Anthropometric measures, including BMI and waist circumference, were recorded, with overweight and obesity defined as BMI ≥25 kg/m² and ≥30 kg/m², respectively. Weight history data were collected via self-reports, including weight changes over time and attempts to lose weight.

Statistical analysis involved the use of linear regression, variance adjustment for complex sampling, and analyses stratified by age, gender, and demographic factors.

Results and discussion

Average adult BMI was found to be 29 kg/m², with males generally weighing more than females. A third of adults each were classified as normal weight, overweight, or obese. About 30–50% of participants had attempted weight loss in the past year, with higher rates among females. Whole milk intake was found to be inversely associated with body weight, BMI, and waist circumference in most groups.

For adults aged 20 years and above, each cup-equivalent (cup eq) of whole milk was linked to a 0.5 kg/m² decrease in BMI, a 1.5 kg reduction in body weight, and a 1.1 cm smaller waist circumference. Whole milk also correlated with a higher prevalence of normal weight (+2.5% per cup eq), lower obesity rates (-3.2%), and elevated waist circumference (-2.2%), except for older females, where statistical significance was not reached. Whole milk was associated with an increased desire to gain weight in some age groups, a nuance worth noting alongside its link to weight loss attempts.

Health Risks: Obesity is a major risk factor for noncommunicable diseases such as cardiovascular diseases, diabetes, musculoskeletal disorders, and some cancers.

Daily milk consumption was more common in childhood (86-88%) than in adulthood (47-55%), declining with age. Interestingly, whole milk intake was associated with increased attempts to lose or gain weight but was inversely related to a desire to maintain current weight. These associations were consistent across age and gender groups after adjusting for factors such as ethnicity, income, physical activity, and smoking.

The findings suggest that whole milk may be beneficial in healthier body weight profiles and reduced central obesity risk, challenging the perception that full-fat dairy may contribute to weight gain. Residual confounding cannot be ruled out, as the study relied on observational data, and other dietary patterns may also play a role in these associations. Gender and age differences highlight the need for individualized dietary recommendations.

The study is strengthened by the use of a large, nationally representative dataset with extensive covariate adjustments. However, the study's cross-sectional design prevents causal inferences, reliance on self-reported data introduces potential bias, and the narrow range of whole milk intake and unexamined milk fat levels limit broader conclusions.

Conclusion

In conclusion, the study suggests that whole milk intake is linked to lower body weight and reduced obesity risk in a large, nationally representative sample of American adults, consistent with prior research.

These results could potentially inform future dietary guidelines and public health strategies. Further exploration into the mechanisms behind whole milk's effects on weight and long-term clinical trials across diverse populations is necessary to validate these findings.

Journal reference:

• Torres-Gonzalez, M., Pikosky, M. A., Ricklefs-Johnson, K., Fulgoni, K., Fulgoni, V. L., Agarwal, S., & Cifelli, C. J. (2024). Whole milk intake is associated with lower body weight and body mass index in American adults. Nutrition Research.DOI: 10.1016/j.nutres.2024.11.002, https://www.sciencedirect.com/science/article/pii/S0271531724001453