- Carb and fat blockers are substances that interfere with the digestions of carbohydrates and fats.
- There are no studies showing these supplements help you lose weight—they only help you limit fat gain while overeating.
- Generally speaking, supplements that do this are not very effective and are easily abused.
The Holy Grail of Fat Burning.
A supplement that you can take once a day and will prevent you from getting fat despite allowing you to eat anything you want. That magic bullet to shoot away all your problems and, hopefully, not kill you at the same time.
It doesn’t exist right now unfortunately, but that hasn’t stopped researchers from trying to discover it.
And even if the researchers haven’t discovered it, it definitely doesn’t stop marketers from trying to sell it to you.
There are many ideas that have popped up when it comes to how such an amazing theoretical fat burner could work and one of them, the topic of this article, has quite a simple premise . . .
What if you just didn’t absorb the calories you ate? In one end and out the other?
Carb and fat blockers are a sub-genre of fat burners dedicated to preventing calorie uptake and have been studied, well, not extensively, but they do have evidence behind them.
Only one problem, they don’t always block calories alone. They sometimes block nutrients as well.
Are they worth your consideration? Do the benefits of absorbing fewer calories outweigh the hazards of absorbing fewer nutrients? Are some better than others?
Well, read on so you can learn something new before I once again proceed to crush your hopes and dreams.
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- What Are Carb and Fat Blockers?
- How Do Carb and Fat Blockers work?
- What Supplements Are Nutrient Blockers?
- White Kidney Bean (Phase 2)
- Salacia reticulata
- Psyllium Husk
- Do Carb and Fat-Blockers Work for Fat Loss?
- Are Carb and Fat Blockers Safe?
- Fat Malabsorption
- Carbohydrate Malabsorption
- Protein Malabsorption
- The Bottom Line on Carb and Fat Blockers
Table of Contents
Carb and fat blockers are a group of supplements and food components that, put simply, block carbs and fats from being absorbed. Technically protein blockers exist but, due to the importance of dietary protein, they aren’t made into supplements.
Carb and fat blockers have always existed in various foods as a constant evolutionary battle between us humans and the things we enjoy eating.
Nutrients are vital to plants and they want to hold on to them so they try everything they can to prevent other creatures from stealing or digesting their beloved nutrients.
Us, being those other creatures who want to steal nutrition for ourselves, adapted our intestines to break down and digest a ton of various food products. Our intestines are not infallible, however, and sometimes the plant compounds win out.
When we find something that prevents us from absorbing the nutrients we call it a “nutrient blocker,” then can further specify what it blocks (carb blocker, fat blocker, etc.), since us humans are egocentric and those are supposed to be our nutrients you damn soybeans . . .
If we can’t absorb something from the intestines, we cannot store it in our tissues and we’ll simply poop it out.
There are ways to mitigate these blockers or destroy them, releasing the nutrients for our bodies, but there may also be times where we actually do want this blocking ability; namely as an emergency switch in times of gustatory hedonism.
In other words, if you want to eat a lot of carbs and fat but don’t want to absorb it.
And knowing how they work is the first part of the battle.
Any sort of carb or fat blocker in the intestines will work in one of two ways:
- There will be an enzyme that’s vital in digesting a macronutrient, and the blocker will target and keep it from doing its job. This is indirect inhibition or enzymatic inhibition (since we usually target enzymes.)
- The blocker will, itself, seek out and bind to the carb or fat molecule. When the blocker and target are connected, the target can’t be absorbed. This is direct inhibition.
Most carb and fat blockers work by enzymatic inhibition, since both carbs and fat rely on several different enzymes to be digested properly. (Enzymes are special proteins that help metabolize nutrients.)
This is because macronutrients are big and they need enzymes to break them down a bit before getting absorbed. Compared to the macronutrients, and in their literal name, micronutrients are smaller and sometimes don’t need to get “treated” in any way before absorption.
(Truth be told the “macro” and “micro” refer to how much are needed in your diet, needing dozens of grams of the macros and milligrams of the micros, but it’s also oddly accurate for the molecular size of them as well).
When it comes to dietary supplements we mostly see the enzymatic inhibition since nobody really wants to prevent vitamin absorption. They just want to inhibit carbohydrate and fat absorption.
How well do these compounds work, though? Well, let’s take a look.
There are a few supplements that you may see here and there that aim to “prevent weight gain from food” and, while they tend to have a kitchen-sink approach to things (throw in everything under the sun) there are a few more common and interesting options out there.
The main ones are:
- White kidney bean extract (Phase 2)
- Salacia reticulata
- Psyllium Husk
White kidney bean extract is the name for the plant Phaseolus vulgaris, and it’s been used as a dietary supplement under the brand name “Phase 2” for quite some time. It was perhaps the first valid carbohydrate inhibitor to enter the market for the purpose of preventing fat gain.
It works by blocking the α-amylase enzyme, the enzyme that mediates the digestion of starch.
Unfortunately, these studies are confounded with the fact the the producers of the supplement funded many of them. Sometimes this isn’t a concern, namely when other research groups replicate it as well, but independent evidence on this topic is not common.
The subjects also often report gastrointestinal side-effects like flatulence, cramping, and diarrhea.
While white kidney bean extract can potentially lessen fat gain from eating starchy foods, studies in humans seem to have a potential conflict of interest with the manufacturer.
While there are many herbal compounds that interact with carbohydrate digestive enzymes, Salacia reticulata is one that affects the widest range of carbohydrate digesting enzymes with a considerable degree of potency.
Sugar digesting enzymes maltase, sucrase, and isomaltase are all inhibited by two compounds in this plant known as salacinol and neosalacinol to a potency that’s slightly less than acarbose; a pharmaceutical reference drug.
There are many other compounds in this plant that are effective as well, it’s just chock full of carbohydrate-inhibiting molecules.
Salacia reticulata has been noted to reduce glucose absorption in rats and, subsequently, reducing both glucose absorption and subsequent insulin secretion in both type II diabetics and otherwise healthy adults.
It can help reduce absorption from a single dose, and may be useful in managing prediabetes or kidney disease, but by design it can’t be more curative than simply not consuming the carbs in the first place.
Salacia reticulata is a promising carbohydrate absorption inhibitor but it’s about as promising as a triangular wheel. Technically it could work and it could work well, but it’s a triangular wheel, why opt for that when there are clearly better ways to tackle the issue at hand?
Psyllium husk is a relatively balanced mix of both soluble and insoluble fiber.
Soluble fiber dissolves in water and tends to soften stool while insoluble fiber tends to bind to fatty acids and help your stool move along your intestines at a reasonable pace.
Psyllium is a pretty healthy thing to have in your diet and tends to be the “go-to” fiber supplement for when your diet isn’t providing enough. It seems to reduce the amount of carbohydrate absorbed slightly, increase fecal bile acids, but doesn’t seem to reduce fat absorption much.
It’s still nifty though, since it increases butyrate levels in the feces (which shows it might be good for your gut bacteria) and, oddly enough, might reduce flatulence. That’s a weird one since most fibers increase it.
Ultimately, psyllium husk seems to have minor carbohydrate blocking potential but is unique in the fact that it seems to not be associated with the expected side-effects of such an action (flatulence).
Generally speaking these technically work for fat loss (as evidenced by Orlistat, a pharmaceutical fat blocker) but are often seen as a horrendous option for many reasons:
- They can’t cause fat loss, but can only prevent fat gain. This means they don’t provide any more benefit than fork put-downs and table push-aways do.
- They reinforce bad habits since many users think they can get away with eating junk food. Even if you negate 20 percent of the weight gain you still have to deal with the other 80 percent.
- Their potency and side-effects go hand-in-hand. It’s damn near impossible to get a very potent macronutrient (carb or fat) blocker and avoid the side-effects they bring.
They hold some benefit in people who don’t want to lose weight but want a wee bit of management, like sipping some salacia tea alongside breakfast to lessen an increase in blood glucose, but potent and side-effect free fat burners they are not.
When it comes to major side-effects then, yes, the majority of them (and all listed in this article) are “safe” in moderate quantities. Safe, in this sense, refers to not causing any major or long-term adverse health effects.
However, just because they’re medicinally safe doesn’t mean they’re without side-effects. Blocking carbs and fats comes with a whole host of side-effects.
Fat malabsorption is perhaps the most, umm, “prominent” nutrient to see whether or not it’s absorbed after you’ve done your business. You just get lipid pools in the toilet like a few tablespoons of olive oil in a pot of water.
It’s also one of the more relevant ones since, to put it lightly, unabsorbed fatty acids tend to act like intestinal lubricant.
The chyme you have in your intestines, “chyme” being the polite way to refer to what was once food and what will soon become feces, normally takes quite a long time to pass and there’s a slow rate of nutrient absorption during this time.
Malabsorbed fatty acids lube it up and, when a mass movement occurs (scheduled intestinal contractions to keep everything moving along) the chyme could just slip-slide away towards the end.
It’s why you commonly see lipase inhibitors in “detox” plans since if you dump the five pounds of waste in your gut in one day it looks like fat loss on the scale, and also why the first pharmaceutical intervention for lipase inhibition (Orlistat) resulted in people having embarrassing “accidents” with higher than normal frequency.
Having a bit of lipase inhibition in your diet isn’t a big deal, but do take care to pair it with insoluble and soluble fiber so you can “bind” the lipids together in the chyme. If you don’t, and you take both potent lipase inhibitors and a lot of fatty acids together, then you better hope you’re not kept away from a washroom for more than 30 minutes at a time.
Furthermore, if the chyme gets sped up then it could impair the absorption of other nutrients, since they simply have less time to be absorbed. If protein has less time to digest then, as you’ll soon find out, it can cause the smell situation to drastically increase.
Not many other side-effects beyond shitting yourself in a highly smelly manner, though.
Carbohydrate malabsorption tends to result in side-effects related to gas production (flatulence and cramping).
Gas is produced in the intestines by bacteria that happily eat up nutrients and, as a by-product, produce gas that builds up. Some will get incorporated into chyme and, along with water, give it “fluffiness”, making it easier to pass, but sometimes it’s just gas that’s passed.
A healthy diet will always have a degree of flatulence, and truth be told some flatulence here and there can be a sign of a healthy diet and a happy intestinal tract. However, that farting should be coming from intestinal bacteria digesting and eating fibers and prebiotics.
When a large amount of carbohydrates go unabsorbed in the small intestine they can pass to the large intestine, giving the bacteria there an absolute feast.
Overabundance of gas production here will then lead to an increase in pressure (you colon acts like an over-inflated bike tire) pushing on the intestinal walls; cramping and pain come from this and, subsequently, your body relieves this gas buildup by opening the backdoor.
Protein malabsorption is pretty common when you consume a large amount of fast-absorbing protein in a single sitting.
Protein absorption does have a “rate-limit” of some degree since absorption can only work so fast, but it’s reasonable to assume that the body adapts to a degree when exposed to different daily levels of protein intake.
If you consume more protein in one sitting then that’s fine. The intestines will simply take more time digesting it to the point where even 50 grams at once can be handled. However, a rule of thumb is that the faster a protein is absorbed the faster it’s removed from the body.
Protein malabsorption that comes from trypsin inhibitors (like those in raw soy beans) or, more commonly, just eating too much protein at once isn’t too unhealthy nor does it cause too many intestinal problems (perhaps a slight increase in diarrhea), but oh dear god it smells.
This is because proteins, composed of amino acids, are the source of dietary nitrogen. While amino acids themselves may not smell overly bad there are various small-weight nitrogen compounds that are produced by digested amino acids that are absolutely horrendous.
We’re talking stuff like putrescine (named after “putrid”) and cadaverine (named after “cadaver”) that were first discovered by asking the question, “Why does this rotting fish smell so bad?”
Furthermore, if the diet has a large amount of sulfur-containing amino acids (cysteine, methionine, and taurine) that aren’t absorbed then it could also give it an “eggy” scent.
Ultimately, unless you want to compete with your friend who has Crohn’s disease on who can incapacitate a healthy bull with their farts first, then try your best to absorb your protein.
At the end of the day, carb and fat blocking supplements are probably going to always be on the shelves since they’re one of the closest things marketing has to the “magic bullet” of weight loss that allows you to eat as much as you want—in theory.
They can have some benefits in reducing weight gain during high caloric times but, for the purpose of fat loss, they are imperfect bandages that encourage bad habit formation.
Somebody who continually seeks out carb and fat blockers in an attempt to lose weight is somebody who’s either unable to, or unwilling, to eat less food or make more practical changes to their lifestyle to achieve their goals.
Furthermore, the more effective carb and fat blockers are, the more intestinal side-effects they cause. There’s no way a macronutrient blocker can be highly effective without causing great discomfort to the intestines and possibly damaging them long-term.
So ultimately, they’re a crutch but a crutch that actively prevents your leg from healing.