Poor Gut Microbiota Makes Weight Loss Harder? Get These 6 Small Things Right First
This article is for health education purposes only and is for informational reference only; it does not constitute medical advice. If you have health concerns, please consult a professional doctor.
On those days when the number on the scale gets stuck, many people's instinctive reaction is to "eat a little less."
But there is one often-overlooked thing: the hundreds of trillions of bacteria in your gut are also taking part in the question of "whether to store energy as fat."
They are not to blame, and they can indeed be fed. The 6 things below can start with your next meal today.
First, Two Sets of Numbers
20 adults with stable body weight checked into a metabolic ward and ate the same ingredients, the same calorie density, the same sugar, salt, and fiber, divided only into "ultra-processed" and "minimally processed" versions, eating freely until full. Result: during the two ultra-processed weeks, they ate 508 extra kcal per day and gained 0.9 kg in two weeks; switching to the two minimally processed weeks, they lost 0.9 kg again[4]. Same kitchen, same group of people, the only difference was how much the food was processed.
The other set of numbers comes from probiotics: 15 randomized trials, 957 people, taking them on average for 3 to 12 weeks, lost 0.60 kg more than the placebo group, had 0.60 percentage points more reduction in body fat percentage, with no significant difference in fat mass[5]. It works, but the magnitude is very small and cannot support the words "weight loss plan."
6 Things, Do Them One by One
1 Get Fiber to 25 to 29 Grams First
A pooled analysis of 185 prospective studies plus 58 clinical trials found: the group eating more fiber had 15% to 30% lower all-cause and cardiovascular mortality, and also fewer cases of coronary heart disease, stroke, type 2 diabetes, and colorectal cancer; the magnitude of risk reduction reached a relatively large value in the range of 25 to 29 grams per day[1]. In reality, most people do not even get half of that.
The method is simple: base breakfast on oats or mixed beans, have one serving of vegetables at lunch and dinner each, and replace half of the staple food with whole grains. No need to buy powder, no need to do the math.
2 One Serving of Fermented Food Every Day
A 17-week randomized trial, 18 people in each of the two groups. The fermented food group (yogurt, kefir, kimchi, kombucha, etc., with amounts gradually increased) had steadily rising microbiota diversity, and 19 inflammation-related proteins decreased, including interleukin 6; the high-fiber group's microbiota diversity did not change much, but the enzymes that break down plant fiber increased[2].
In other words: fiber delivers food to the bacteria, fermented foods directly supplement the person. The two do not conflict; eat them together.
3 Count Plant Variety Once a Week
Stool samples from more than 10,000 volunteers showed: the richer the variety of plants in the diet, the more obvious the differences in microbiota and metabolites; while using labels like "vegetarian or not" to explain it actually had little explanatory power[3].
Over a week, count how many kinds of plants you have eaten: grains, legumes, vegetables, fruits, nuts, mushrooms, and spices all count. Most people, once they count, discover that they only regularly eat those seven or eight kinds. Variety is easier to change than quantity.
4 Change Ultra-Processed Foods From "Every Day" to "Occasionally"
The source of the 508 kcal number is the trial at the beginning[4]. Ultra-processed foods are not "toxic," but they are too soft, too fragrant, too fast—eating until full the same way, you will eat more.
The way to judge is very crude: turn to the ingredient list; a long string of incomprehensible chemical names plus emulsifiers, flavorings, and sweeteners means it is one. Downgrade it from a daily fixed item to an occasional item once or twice a week.
5 Do Not Treat Probiotic Capsules as Weight Loss Drugs
An effect size of 0.60 kg is often wiped out by a single social meal in real life[5]. Capsules are more suitable for specific scenarios, such as short-term supplementation after antibiotic use; whether to use them and for how long, it is recommended to ask a doctor. They are not the main line of weight loss; the main line is still eating, moving, and sleeping.
6 Give the Microbiota More Than 10 Weeks
The changes in the fermented food group gradually appeared within 10 weeks, and the entire study ran to 17 weeks[2]. The microbiota is not a switch; it is more like a plot of land—when you change the fertilizer, you have to wait for a crop cycle. The review states it very clearly: diet and probiotics can indeed regulate the microbiota, but individual differences are large, so do not expect any single food to solve all problems[6].
Most people fail at two things: they stop after two weeks without feeling anything; or they change five things at once and cannot keep it up. Pick one thing and do it for a full month first.
Three Things You Can Do Today
One, add a serving of fermented food to breakfast—unsweetened yogurt or a small dish of kimchi will do.
Two, tonight spend two minutes writing down the kinds of plants you have eaten this week, and add 3 kinds next week.
Three, before buying snacks, take a look at the ingredient list; if it has more than five lines and is all unfamiliar names, put it back.
Weight is the result, the microbiota is the soil. The soil changes slowly, but it does indeed respond to your daily choices.
Suggest forwarding this to that friend who "doesn't eat much but still can't lose weight," and go through the 6 things together.
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Disclaimer: This article is for health education purposes only and is for informational reference only; it does not constitute medical advice. If you have health concerns, please consult a professional doctor.
Conflict of interest statement: This article does not involve any product recommendations or commercial collaborations, and the author has no conflict of interest with the research institutions mentioned in the text.
© 2026 Sun Sheng Hua (Beijing) Medical Technology Co., Ltd.
References
[1] Reynolds A, Mann J, Cummings J, Winter N, Mete E, Te Morenga L. Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. Lancet. 2019;393(10170):434-445. PMID: 30638909
[2] Wastyk HC, Fragiadakis GK, Perelman D, et al. Gut-microbiota-targeted diets modulate human immune status. Cell. 2021;184(16):4137-4153. PMID: 34256014
[3] McDonald D, Hyde E, Debelius JW, et al. American Gut: an Open Platform for Citizen Science Microbiome Research. mSystems. 2018;3(3):e00031-18. PMID: 29795809
[4] Hall KD, Ayuketah A, Brychta R, et al. Ultra-Processed Diets Cause Excess Calorie Intake and Weight Gain: An Inpatient Randomized Controlled Trial of Ad Libitum Food Intake. Cell Metab. 2019;30(1):67-77. PMID: 31105044
[5] Borgeraas H, Johnson LK, Skattebu J, Hertel JK, Hjelmesaeth J. Effects of probiotics on body weight, body mass index, fat mass and fat percentage in subjects with overweight or obesity: a systematic review and meta-analysis of randomized controlled trials. Obes Rev. 2018;19(2):219-232. PMID: 29047207
[6] Valdes AM, Walter J, Segal E, Spector TD. Role of the gut microbiota in nutrition and health. BMJ. 2018;361:k2179. PMID: 29899036