Some types are sold as weight loss supplements. They’re made from a group of compounds called alpha-amylase inhibitors, which occur naturally in certain foods.
These compounds are usually extracted from beans and are referred to as Phaseolus vulgaris extract or white kidney bean extract. Others come in the form of prescription medications called alpha-glucosidase inhibitors (AGIs), which are used to treat high blood sugar in type 2 diabetics, In this article, the term carb blocker will refer to the nutritional supplement containing bean extract, not the prescription medications.
The studies ranged from 4–12 weeks long and people taking carb blockers usually lost between 2–5.5 lbs (0.95–2.5 kg) more than the control groups. One study showed up to 8.8 lbs (4 kg) greater weight loss than the control group.
Interestingly, the people who ate the most carbs appear to be the same ones who lost weight while using these supplements.
This makes sense because the higher the proportion of complex carbs in your diet, the bigger the difference carb blockers can make.
However, the average weight loss for those eating a carb-rich diet was still just 4.4–6.6 lbs (2–3 kg), on average.
Carb Blockers May Decrease Appetite
In addition to blocking carb digestion, carb blockers may affect some of the hormone involved in hunger and fullness. They may also help slow stomach emptying after a meal.
One reason for this effect may be because bean extracts also contain phytohaemagglutinin. This compound can increase the levels of some hormones involved in fullness.
One rat study found that the phytohaemagglutinin in carb blockers did cause a significant decrease in food intake. The rats that had been given the compound ate between 25–90% less. However, this effect lasted only a few days.
However, there may be other ways that carb blockers decrease appetite.
Similar studies found that a carb blocker supplement could decrease the amount of food the rats ate by 15–25% over a consistent period of time and even caused them to eat less of foods that are high in fat and sugar . This effect has not been well-researched in humans, but one recent study found that a concentrated, standardized bean extract did decrease feelings of hunger, probably by suppressing levels of the hunger hormone ghrelin.
Carb Blockers May Help Control Blood Sugar
Carb blockers are usually marketed as weight loss supplements, but they probably have a bigger impact on blood sugar control. They prevent or slow down the digestion of complex carbs. As a result, they also lower the spike in blood sugar levels that would normally happen when those carbs are absorbed into the blood stream.
However, this is only true for the percentage of carbs that are actually affected by the carb blockers.
In addition, carb blockers are thought to affect some of the hormones involved in controlling blood sugar levels.
In several studies of healthy people, carb blocker supplements have been shown to cause a smaller rise in blood sugar after consuming a meal high in carbs. They also cause blood sugar levels to return to normal faster.
Beneficial Resistant Starch
Carb blockers have another unintended benefit — they increase the amount of resistant starch in the large intestine. This is because they decrease the amount of carbs that are absorbed in the small intestine, thereby increasing the starch that runs through the gut.
Similar to fiber, resistant starches are any starches in food that cannot be digested by the enzymes in the small intestine.
They are found in foods such as raw potatoes, bananas legumes and some whole grains. When resistant starches pass into the large intestine, gut bacteria ferment them and release gasses and beneficial short chain fatty acids.
When carb blockers prevent the digestion of complex carbs in the small intestine, these carbs function like resistant starches.
Many studies have associated resistant starch with decreased body fat, healthier gut bacteria and improved blood sugar control and insulin sensitivity. Additionally, resistant starches may help increase the amount of fat your body burns after a meal.
Are Carb Blockers Safe?
Carb blockers are generally considered safe, but make sure to buy them from a reputable source.
As far as side effects are concerned, carb blockers are considered very safe.
However, when carbs are fermented by bacteria in the large intestine, the gasses they release can result in a number of uncomfortable side effects.
These can include diarrhea, bloating, flatulence and cramping.
These side effects are usually not severe and go away with time, but they are enough for some people to stop taking carb blockers.
Additionally, people with diabetes who take insulin should talk to a doctor before taking carb blockers, since there is a chance they could cause low blood sugar if the insulin dose is not adjusted.
Another issue is supplement regulation.
Supplement manufacturers are themselves responsible for the safety and integrity of their products, and there have been many cases of fraud in the supplement industry.
The FDA recently inspected several herbal supplements and found that a mere 17% of the products contained the main ingredient listed on the label.
In the past, the FDA has even found dietary supplements that were adulterated with prescription medications that had previously been removed from the market due to their dangerous side effects.
These potentially harmful medications had been added in an attempt to make the supplements more effective.
For this reason, chances are that many of the carb blockers you can buy in the store don’t actually contain what is listed on the label.
When it comes to supplements, it’s always a good idea to do some research and buy from a reputable manufacturer.