Gut bacteria can make you fat. Beware of pre- and probiotics

Believe it or not, but gut bacteria can actually cause fat gain. They really aren’t all that healthy as all the pre- and pro-biotic vendors make them out to be either.

Not all gut bacteria are bad though, but even the good ones can contribute to fat gain.

For instance, gut microbiota protects the body against pathogens, strengthens the immunity, develops intestinal microvilli, degrades non-digestible polysaccharides (fermentation of resistant starch, oligosaccharides, inulin), neutralizes the activity of dietary carcinogens, such as nitrosamines, reduces TLR4 (endotoxin receptor) expression, etc (1, 2, 3).

However, an excess promotes the creation of endotoxins and subsequent inflammation, too much short-chain fatty acids, lactate (which is a metabolic burden), excess fat gain (adipose tissue hypertrophy, instead of hyperplasia), gas production, bloating, intestinal inflammation, Periodontitis, insulin resistance, choline deficiency (gut bacteria break down choline, thus mimics a choline-deficient diet), fatty liver, fermented toxic amino acid derivatives (such as cresol, phenyacetate, indole), etc. (4, 5, 6).

So we want to have as little gut bacteria as possible, but in the right ratio to still harvest the benefit of the good gut bacteria (7).


So how do gut bacteria promote fat gain?

In this following study we see that germ-free mice (mice without any gut bacteria), had about 40% less total body fat than mice with a normal gut microbiota, even though the latter ate 30% less food than the germ-free mice (8). These bacteria-free mice were also significantly more active than the mice who had gut bacteria. Anti-biotic treatment in humans is also shown to have a similar action of speeding up the metabolism.


So gut bacteria promotes fat gain in five distinct ways. Gut bacteria:

  1. Inhibits fasting-induced adipocyte factor (Fiaf). Fiaf is an inhibitor of lipoprotein lipase (LPL). LPL increases the intake of fats into the adipose tissue and promotes fat formation and storage. Fiaf also promotes PGC-1α, which promotes the oxidation of fats as well as the formation of new mitochondria. Higher Fiaf (due to less gut bacteria), would stimulating fatty acid oxidation and uncoupling (9).
  2. Suppresses AMPK. AMPK promotes the oxidation of fats (by lowering malonyl CoA and increasing carnitine palmitoyl transferase-1 (CPT-1)) and speeds up the metabolism and promotes fat loss.
  3. Increases the production of short chain fatty acids that are substrates for lipogenesis, which creates fat for storage. Obese people have an overproduction of short-chain fatty acids (10).
  4. Promotes the expression of genes the promote lipogenesis, such as carbohydrate response element binding protein (ChREBP) and sterol response element binding protein 1 (SREBP-1).
  5. Reduces leptin and adiponectin, as well as lower the NAD:NADH ratio. A low NAD:NADH ratio would lead to higher cortisol, more lactate formation, impaired energy production, low steroidogenesis, fatigue, greater free radical production, insulin resistance, slow metabolism, etc.

So an excess of gut bacteria is totally undesirable, even if they are “good” or “bad”. We want low total gut bacteria, but with a good ratio of the good ones to the bad ones.

How do we control the ratio?
Eating a healthy diet with whole foods and avoiding processed and high polyunsaturated fatty acid laden foods, would automatically cause the ratio to be in favor of the “good” gut bacteria. However, an excess (or even a little in “sensitive individuals”) of fibrous foods could also cause an overproduction of gut bacteria.

Foods like cocoa, coconut oil, raw honey (unfiltered), milk, and fruits will change it to a more favorable ratio.

If you plan on promoting good bacteria with pre-biotics or pro-biotics, do so carefully, as even the good bacteria promote the concentrations of lactate and SCFA as well as suppress FIAF and can promote fat gain (11).

A quick and effective way to clean out the gut is to take 3-4 tbsp of activated charcoal once a week for a month with a pinch of cascara sagrada and 1 tbsp of MCT oil or monolaurin. This protocol can be done more regularly depending on how severe your symptoms are.

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