Does 'Daily Yogurt' Have No Diet Effect? Study Reveals the 'Gut Health Trap': Higher BMI Among Those with Gasseri Bacteria

Kintock, operated by SheepMedical Inc., is a gut DNA testing service that enables easy at-home analysis of gut flora.

Kintock uses a machine called a 'next-generation sequencer' to identify and analyze types of gut bacteria. After analyzing data from around 20,000 individuals who underwent gut flora testing, an unexpected finding emerged.

As summer approaches and many become concerned about body shaping, 'yogurt' is often the first food that comes to mind for dieting. However, this time, data revealed a trend contrary to conventional wisdom.

Based on data from approximately 20,000 users of 'Kintock,' a study examined the relationship between 'yogurt consumption frequency' and 'BMI.' It was found that yogurt consumption frequency did not affect BMI distribution, and there was absolutely no correlation between the two.

In other words, the widely held belief that 'yogurt = weight loss or prevents weight gain' was not supported by the data, suggesting it may have no direct effect on dieting.

The survey targeted 13,493 women aged 20 and over who had previously taken the gut DNA test via Kintock.

These 13,493 participants were divided into a 'beauty weight group' and an 'obese group' based on BMI values. The study examined whether trends emerged in relation to the overall composition ratio and responses to the questionnaire item 'frequency of yogurt and dairy beverage consumption,' yielding the following results:

※ Beauty weight group: BMI 17.5–19.0

※ Obese group: BMI 25.0 and above

Regardless of yogurt and dairy beverage consumption frequency, each group's composition closely matched the overall baseline (composition ratio), leading to the conclusion that there is 'no statistical correlation.'

Furthermore, detailed analysis showed that within the beauty weight group, individuals with higher yogurt and dairy beverage consumption had a slightly lower proportion compared to the overall baseline, while those with lower consumption had a slightly higher proportion.

Conversely, in the obese group, individuals with higher consumption had a slightly lower proportion compared to the baseline, while those with lower consumption had a slightly higher proportion.

In other words, contrary to the general perception that 'yogurt = slim or less likely to gain weight,' this survey found 'no statistically significant association (no relationship).' Detailed data analysis even revealed 'an opposite trend.'

What about the relationship between gasseri bacteria and BMI?

We also investigated the relationship between BMI and the presence of 'gasseri bacteria'—commonly believed to reduce visceral fat and aid weight loss—among the same 13,493 women aged 20 and over.

Participants were again divided into beauty weight and obese groups based on BMI, and the study examined trends in relation to overall composition and responses to the yogurt/dairy consumption frequency question, resulting in the following:

This survey revealed a 'U-shaped' distribution: gasseri bacteria levels were lowest among individuals with standard BMI (19.0–21.0), while both the beauty weight group (17.5–19.0) and the obese group (25.0 and above) showed higher-than-average detection rates. The data clearly shows that the simple assumption 'more gasseri bacteria = thinner' does not hold.

Moreover, detailed analysis revealed that the obese group had a 1.5 times higher detection rate of gasseri bacteria than the beauty weight group—'a completely opposite trend' to the common belief that 'gasseri bacteria = weight loss.'

This study revealed results contrary to popular belief: 'no correlation between yogurt consumption frequency and BMI,' and 'higher prevalence of gasseri bacteria among high-BMI individuals.' Two possible reasons for this unexpected reality are speculated:

Cause 1. 'Reversed causality' triggered by health consciousness

Individuals with higher BMI (those concerned about body shape) may be more sensitive to health information from TV and magazines and thus consciously consume gasseri-containing products and yogurt more actively. In other words, it's not that 'gasseri bacteria caused weight gain,' but rather that 'those wanting to improve their physique are taking in more gasseri bacteria for dieting purposes,' resulting in a reversal of causality.

Cause 2. Difference between gasseri bacteria's habitat and the primary organ for fat absorption

In the human digestive system, most fat and calories from food are absorbed in the 'small intestine.' In contrast, gasseri bacteria primarily reside, colonize, and actively function in the 'large intestine,' located further down the digestive tract. Therefore, even if large amounts of gasseri bacteria are present in the large intestine, fat absorption has already occurred in the small intestine upstream, making it difficult for the presence of gasseri bacteria to directly lead to weight loss (lower BMI) due to this physiological mechanism.

Some studies have reported weight loss effects of gasseri bacteria. However, the mechanism is not believed to fundamentally alter intestinal absorption functions, but rather to 'potentially influence the absorption process of dietary lipids under specific conditions.' Therefore, it is inferred that simply consuming gasseri bacteria or merely harboring them in the large intestine, regardless of diet content or timing, does not automatically result in lower BMI.

The real factor strongly correlated with high BMI: 'convenience of food'

More than yogurt or vegetable consumption frequency, the following food consumption items showed an extremely strong positive correlation with high BMI (25.0 and above):

※ Convenience store bento and prepared meals: Among the obese group (BMI 25.0 and above), the proportion of regular users (3+ times per week) was notably high at 34.8%.

※ Fast food: Among the obese group (BMI 25.0 and above), the proportion of regular users (3+ times per week) was 20.5%, a sharp increase from 12.0% in the beauty weight group.

※ Instant foods: Among the obese group (BMI 25.0 and above), the proportion of regular users (3+ times per week) rose to 22.7%.

The data clearly shows that the true cause of obesity is not the lack of specific foods, but the frequent consumption of convenient, ultra-processed foods such as 'fast food,' 'instant foods,' and 'convenience store meals.'

In conclusion, this survey highlights that relying solely on an 'additive health approach'—such as 'eating yogurt leads to weight loss' or 'consuming trendy gasseri bacteria is beneficial'—is insufficient for maintaining an ideal body shape or healthy BMI.

Therefore, based on our data from nearly 20,000 individuals, we strongly recommend adopting a 'subtractive dietary approach'—specifically, reducing ultra-processed foods first. Focusing on the following points is the most reliable shortcut to effective dieting and gut environment improvement:

〇 Do not seek a 'free pass' from specific 'health foods'

Instead of reassuring yourself with 'it's okay because I'm eating yogurt,' take a holistic view of your entire diet and address fundamental calorie and nutritional balance.