My little diet experiment

SucArch

Hello everyone!
Some time ago, I conducted a small experiment to understand how dietary fiber affects satiety, the development of gut microbiota (the community of microorganisms in the intestines), and their influence on blood glucose "spikes," as gut bacteria participate in digesting up to 80% of food. To briefly summarize the experiment: For two weeks, I ate the same dishes supplemented with dietary fiber, measuring my weight and blood glucose levels every morning:

My Diet

It consisted of: boiled noodles with fried mushrooms and meat, plus sandwiches (bread topped with a small amount of mayonnaise, then cheese, tomato, another layer of mayonnaise, and more cheese). This lasted two days and cost approximately 350 rubles per dayday (Russia, Moscow).

Fiber Types

Fiber comes in two types: soluble and insoluble. Soluble fiber includes several varieties, but I chose the following for myself:

Additionally, I consumed bran (rye or oat). Among insoluble fibers, I took chitosan (a substance derived from crustacean shells) and CMC fibers (carboxymethylcellulose).
To support microbiota growth, carbon and nitrogen are also needed. While fiber provides carbon, nitrogen sources include protein (meat, legumes, or sports protein supplements).

Mini-Experiment

I typically wake up at 6 a.m. During winter, I decided to work on discipline: before breakfast, I weighed myself with an empty bowel and measured my glucose level. Then I took bran, 1–1.5 grams of glucomannan gum with 1 gram of CMC fibers, and chitosan. Over the next 1.5 hours, I measured blood glucose at intervals. For breakfast, I ate noodles with mushrooms, meat, and sandwiches. At the time, I worked as a bike courier from 10 a.m. to 5–6 p.m., usually eating nothing during this period. Dinner was after 6 p.m. Before dinner, I took bran, 1 gram of inulin with 1 gram of CMC fibers, and chitosan. I had my final meal around 9 p.m., again with sandwiches, but beforehand, I consumed bran, 2 grams of pectin, and chitosan. All measurements were recorded in Excel:

A brief explanation of the chart: bars represent weight, while the line shows the average percentage change in glucose levels. Compare the two charts below. A sharp rise and fall in blood glucose indicates high carbohydrate density (the ratio of carbs to food weight), causing faster absorption and renewed hunger. This is precisely why I began losing weight—I ate less because I felt full longer.

Initially, I aimed to test how increasing microbiota diversity through varied fibers would affect glucose levels. Later, I realized carbohydrate density also plays a major role. Reducing it by adding fiber allows decreasing total food intake while staying full longer.
Excel calculations file.

Nutriom System

Long ago, I created a detailed Excel table calculating needs for proteins, fats, carbohydrates, vitamins, and micro/macronutrients based on Russia’s Methodical Recommendations MR 2.3.1.2432–08 by Rospotrebnadzor (Federal Service for Surveillance on Consumer Rights Protection):

Next, I used chemical composition data from Soviet-era food industry textbooks:

The diet planner duplicates data on the main page:

Let’s examine the main page closely. Many cells include comments with detailed descriptions when hovered over:

In the “Diet” section, you can select preferences:

The “Product” section includes a search feature—start typing a name and click the arrow to see matching items from the “Chemical Composition” sheet:

There’s also a reference protein profile, defined by specific amounts of essential amino acids (building blocks of proteins that the body cannot produce itself) required for human health. It has high bioavailability (ease of absorption) and an optimal amino acid ratio for growth, recovery, and overall health.
Here’s a standard reference protein composition based on FAO/WHO recommendations:
Valine: 5.0%
Isoleucine: 4.0%
Leucine: 7.0%
Lysine: 5.5%
Methionine: 2.5%
Threonine: 4.0%
Tryptophan: 1.0%
Phenylalanine: 3.0%

Primary Causes of Obesity

Obesity is not merely a cosmetic issue but a complex metabolic condition now a global epidemic. According to WHO data, 1 in 8 adults (2.5 billion people aged 18+) suffers from it. The root lies in a conflict between our evolutionary past and modern lifestyles. The human body evolved under periodic famine, where fat storage (an energy reserve) was crucial for survival (Source). Today, we live in an environment of calorie abundance and sedentary habits. Ancient mechanisms that once saved us from starvation now work against us, promoting fat accumulation.

Nutrition

Modern diets contain two dangerous components. First: simple carbohydrates (sugar, white bread, sweet drinks). Their consumption causes rapid blood glucose spikes, prompting the pancreas to release insulin (a hormone regulating blood sugar). Excess insulin shuttles energy into fat cells instead of burning it. Fructose (a sugar component in corn syrup and fruits) is especially harmful. It is metabolized uniquely in the liver: 70–80% is trapped there, where the enzyme fructokinase C rapidly processes it, depleting cellular energy (ATP) and causing oxidative stress. This leads to non-alcoholic fatty liver disease (NAFLD), increases appetite, and disrupts satiety signals. Surprisingly, fructose also increases nutrient absorption area and intestinal permeability (“leaky gut”).
The second dangerous component is an imbalance of fatty acids. Historically, the omega-6 to omega-3 ratio was 1:1. Today, it reaches 20:1 due to sunflower, soybean, and corn oils in processed foods. Omega-6 fatty acids (e.g., linoleic acid) promote inflammation, while omega-3s (EPA and DHA in fatty fish) reduce it. Excess omega-6 causes chronic inflammation, leading to insulin resistance (cells ignoring insulin signals) and obesity. Notably, omega-6 stimulates endocannabinoid synthesis—compounds that increase appetite by activating the brain’s reward system.

Stress and Obesity

Financial or emotional stress activates cortisol (a stress hormone), which:
● Intensifies cravings for sweet/fatty foods
● Causes leptin resistance (when the satiety hormone leptin stops working)
● Suppresses the prefrontal cortex (brain region responsible for self-control)
We have two motivation systems: dopamine/serotonin (reward expectation) and endocannabinoid (pleasure from consumption). In high-stress modern life, calorie-dense food becomes a primary “joy” source, creating a vicious cycle: stress → overeating → weight gain → more stress. Stress disables the brain’s planning center while amplifying ancient reward systems that crave instant gratification from high-calorie foods.

Gut Microbiome

The gut hosts trillions of beneficial bacteria that aid digestion. In obesity, their balance is disrupted:
● Bacteria producing short-chain fatty acids (SCFAs, compounds regulating appetite) decrease
● Intestinal permeability increases, allowing toxins into the bloodstream and triggering inflammation
Bacteria producing butyrate (a SCFA activating gut receptors that stimulate satiety hormones) are especially vital. Obese individuals have 30–50% fewer such bacteria. Stress directly harms the microbiome: reducing beneficial Bacteroides while increasing pathogenic Clostridium, worsening inflammation and appetite control.

Why Weight Loss Is Difficult

Obesity creates a self-sustaining cycle:
1. Excess fat causes inflammation
2. Inflammation leads to insulin resistance
3. Insulin resistance increases fat storage
4. Fat tissue produces less leptin, tricking the brain into feeling hungry
Fat tissue is not inert—it actively releases inflammatory cytokines (signaling proteins) during obesity, causing metabolic inflammation. For example, anti-inflammatory adiponectin levels drop by half, while pro-inflammatory C-reactive protein surges.

Recommendations

⚠️ IMPORTANT DISCLAIMER: This material reflects personal experience and research, NOT official medical advice. Consult a doctor or certified dietitian before changing your diet or lifestyle. Individual biology, allergies, medications, and health conditions require personalized approaches.
Based on my experiment and research, here are my recommendations:
● Reduce simple carbohydrates and fructose (especially in drinks and processed foods)
● Improve omega-6/omega-3 balance (eat more fish, fish oil, chia seeds, flaxseed oil)
● Manage stress through sleep and physical activity
● Increase fiber intake to support gut bacteria (start small, gradually increase)
● Drink 2–3 liters of water daily (fiber absorbs water; soluble fiber forms a gel, insoluble fiber aids bowel movement)
● Eat low-glycemic-load foods (mostly vegetables) before meals
● Aim for moderate weight loss: 1–1.5 kg per week (to prevent loose skin)
Note: Initial 1–2 weeks bring rapid fullness due to fiber fermentation, but hunger may follow due to:
1. Microbiome growth phases: colonization → population expansion (bacteria consume ~15% of calories) → stabilization
2. Peptide YY fluctuations: initial rise (+25%), then drop due to intestinal L-cell adaptation (-18%), later rebound (+35%)
3. Water deficiency: increase intake by 20–30 ml per kg of body weight.
Persistent hunger lasts 3–7 days. Solutions: reduce fiber to let microbiome stabilize or endure. Start with minimal fiber (5 g/day) and omega-3 (1 ml/day). Fiber fermentation produces hydrogen and CO₂, potentially causing diarrhea on days 3–4 (lasting 3–4 days). If this occurs, halve fiber and omega-3 intake for 3–4 days. After 3–4 weeks, abdominal heaviness may appear due to microbiome biomass accumulation. Reduce fiber to 5 g/day and take mild laxatives (e.g., 1 tsp lactulose at night) until symptoms resolve (~1 week). The microbiome stabilizes afterward.
Key insight: The problem isn’t weak willpower but deep biological mechanisms requiring a holistic approach.
These measures help restore energy balance, breaking obesity’s vicious cycle. Success depends on reshaping the environment our bodies evolved in. Globally, obesity (per WHO) isn’t an unsolvable epidemic with proper strategies.

Summary of Stages:

Stage 1 (~Days 1–3): Quick fullness from fiber fermentation; mild bloating/gas possible.
Stage 2 (~Days 4–7): Potential diarrhea (bacterial fermentation releases hydrogen/methane). Reduce fiber to 5 g/day; drink 40 ml water per kg body weight.
Stage 3 (~Days 8–14): Constant hunger due to microbiome growth (consuming 230 kcal/day) and leptin drops. Endure this phase.
Stage 4 (~Days 15–21): Abdominal heaviness from microbiome biomass. Reduce fiber to 5 g/day until resolved. Gradually increase by 5 g every 3 days (max 30 g/day).
Stage 5 (~Days 22–28): Fatigue/dizziness from electrolyte imbalance (zinc, selenium, magnesium, calcium absorption drops). Take multivitamins or mineral-rich foods.
Stage 6 (Month 2+): Stabilized microbiome improves leptin/insulin sensitivity. Adjust diet using the Excel planner. Continue multivitamins for a month; take 1–2 fiber-free days every two weeks.

P.S.

I conducted this experiment years ago. By July, I weighed 119 kg (now 113 kg at 188 cm tall) and aim to reach 90 kg by May 2026 without drastically changing my diet.

AnnPT77

Interesting experiment.

I agree with you that fiber is important. There's obviously evidence that gut microbiome diversity tends to be positive for health improvement. When it comes to microbiome, findings more specific than that are IMO still thin and not much replicated IMO, though I don't pretend to be a professional in evaluating the research.

I get that this was an experiment, but I feel it's probable that some uncontrolled features here will hinder applicability to most people in the real world.

Honestly, you started with a base diet that looks pretty appalling to me nutritionally. The mushrooms and tomatoes are your only produce. In the US, some of the other things - bread, pasta - might be "enriched" with added vitamins. I don't know whether that's true in Russia.

You took multi-vitamins sometimes, sounds like. Getting micros from supplements is not the same as getting them from food (often less beneficial).

I'm sure some of that strategy was to facilitate experimental conditions, but honestly I think it's a terrible way to eat, and that people seeing this will get the wrong idea. On top of that, it's been well-demostrated IMU that eating more whole foods has a higher TEF and in most cases improved satiety rather than eating refined or highly processed foods like white bread and white pasta.

I generally agree with your n=1 subjective findings, that increasing fiber results in feeling more satiety so eating less - putting it simply. Yeah, that would facilitate weight loss. But there's honestly real scientific studies out in the real world illustrating the same general idea.

IMO, a better way to reach the "more fiber, better microbiome diversity" outcome is literally to follow standard, mainstream dietary advice: Get some good protein, eat large amounts of veggies and fruits, choose healthy fats, make most grains whole grains. (Maybe that's hard in Russia. It's not hard in the US, though for some the budgetary side of it will require some thought and planning.)

I don't think the downsides you experienced or warn about - bloating, diarrhea, fatigue, dizziness - will need to happen if transitioning more gradually to a higher fiber intake, rather than jumping in all at once. Probably eating a more balanced diet as the basis would help avoid some of them, too. Why would anyone put themselves through that, if it's avoidable?

Also, I absolutely don't think micromanaging forever is necessary: Diet planners, fiber-free days, etc. I doubt that degree of management is ever necessary for most people, TBH.

Also, one specific point: "1–1.5 kg per week" is not "moderate weight loss" for most people. It's extremely aggressive. That's roughly an 1100-1650 calorie daily deficit. There are people - a large fraction of the population - for whom that would be the majority of their TDEE.

Even for me, as a mid-sized woman with relatively high calorie needs for my demographic, that would be around half to three-quarters of my TDEE. For you at 118kg (260lbs) and male, maybe it was OK. But even there, guessing at your other demographic details, I think it's at minimum moderately aggressive, maybe a third to half your TDEE? Losing slowly isn't just about loose skin, it's about health risk. (I actually think the loose skin impact isn't the big deal, but that's a different discussion.)

You mention weight loss as your justification. Bona fides for my n=1 basis for my comments above: I'm female, 165cm (5'5"). My starting weight was 83kg (183 pounds). I lost about 23kg (50 pounds). It took a bit under a year, averaging just under half a kg (one pound) per week, though it was faster at first and intentionally slower at the end. That was over 10 years ago. My blood glucose levels are great. I've remained at a healthy weight since; this morning I weighted about 60kg (131.7 pounds). (You don't give us all the specifics of your case, such as full demographics and timelines.)

My experiences were that the first couple of weeks it took some willpower, probably mainly because of habit-based cravings. I didn't experience any of the forms of misery you mention, except for some fatigue/weakness when I accidentally lost weight too fast at first. (My calorie needs are higher than most calorie calculators estimate: That's why it happened - not intentional. I adjusted as soon as I realized.)

Generally, I just tried to eat close to my moderate-deficit calorie goal, get overall good nutrition, follow a mostly whole foods, protein, healthy fats, veggies/fruits and whole grains way of eating. (That's generally what I recommend to others, though with more nuance and details.)

I wasn't doing a formal experiment, I was trying to dial in a healthier overall life. I worked on it somewhat gradually, though I admit my diet quality at the start was better than many people's so I didn't have to worry as much about phasing in fiber gradually. I didn't and don't use fiber supplements, and only choose other supplements for very specific personal reasons, not generally to make up for poor diet quality.

Thanks for sharing this. I do think it's useful to share, and fascinating, though as discussed above I find some of the details and recommendations problematic, based on a less structured but still n=1 experiment.

Best wishes!