Got Milk? How Your Ability to Digest It Might Be Connected to Your Weight

Sarah Anderson
1 day ago
3 min read

Author: Gerald Cheruiyot

Reviewed by: Sarah Armes and Sarah Anderson

For many adults, drinking milk can result in discomfort, bloating, or other symptoms of lactose intolerance. In contrast, individuals who consume dairy without difficulty are likely to possess a genetic trait known as lactase persistence. Growing scientific evidence suggests that this ability may be associated with a small but measurable difference in body weight.

A large meta-analysis published in BMJ Nutrition, Prevention and Health synthesised evidence from 26 studies to investigate whether genetic differences in lactose digestion are linked to obesity, metabolic health, and milk consumption. The findings indicate a modest but noteworthy association, particularly among adults.

What the Research Revealed

The analysis showed that adults with lactase persistence had a modestly higher average body mass index, approximately 0.22 kg/m2 greater than those without this trait. Although small, this difference was associated with a 27% higher likelihood of being overweight or obese.

Adults who can digest lactose also consumed more milk, averaging around 41 grams per day, equivalent to roughly one-third of a cup. This pattern suggests that higher milk intake, and the additional energy it provides, may partly explain the observed association.

In contrast, no clear association was observed in children, although evidence in younger age groups was limited. The analysis also found no strong link between lactase persistence and metabolic syndrome, which includes risk factors such as raised blood pressure, impaired glucose regulation and abnormal lipid levels.

Why This Association May Exist

The link between lactase persistence and body weight is likely to reflect a combination of behavioural and biological influences. Individuals who do not experience digestive discomfort are more inclined to include milk regularly in their diets, which may lead to higher overall energy intake. Beyond dietary behaviour, emerging evidence suggests that genetic variation in the lactase gene may influence gut microbiota composition and circulating metabolites, with potential effects on energy regulation and fat storage.

It is also important to recognise that the genetic variant most examined in these studies is predominantly found in populations of European ancestry. Other populations around the world have developed different genetic adaptations related to milk digestion, meaning the findings may not be directly transferable across all ethnic groups.

Should You Drink Less Milk

For most people, the answer is no. Dairy products remain an important source of key nutrients, including calcium, vitamin D and high-quality protein. A substantial body of research links moderate dairy consumption with benefits such as improved bone health, better blood pressure control and a reduced risk of certain chronic diseases.

Rather than avoiding milk, the findings emphasise the importance of mindful consumption. For individuals who tolerate dairy well, being aware of portion sizes and overall dietary balance may be beneficial. Body weight is influenced by multiple interacting factors, including physical activity levels, sleep patterns, stress, and overall diet quality, rather than by a single food or genetic trait.

The Bigger Picture: Personalised Nutrition

This research contributes to the expanding field of nutrigenetics, which examines how genetic variation shapes individual responses to food. Although dietary advice can be tailored to lactose digestion, genetics is not yet part of routine practice. Studies such as this reinforce the idea that nutritional responses vary between individuals.

Improved understanding of these genetic interactions may, over time, support more personalised dietary guidance and inform more targeted public health strategies.

Final Thoughts

For individuals who enjoy milk without experiencing digestive symptoms, there is no clear reason to eliminate it from the diet. Instead, these findings serve as a reminder to consider overall dietary patterns and portion awareness. Health is ultimately shaped by balance, and greater awareness of how the body responds to food, whether informed by genetics or personal experience, can support more informed and sustainable choices.

Whether your preference is dairy, lactose-free alternatives or other nutrient-rich foods, the overarching goal remains the same: to nourish the body thoughtfully and enjoy food as part of a balanced lifestyle.