What is a carb blocker

Carb Blockers Guide - What Is a Carb Blocker and How It Works

8 min read


24 May 2019

Carb blockers are a type of diet supplement marketed for people who want to lose weight. You may have read about them online or in the backs of magazines but be unsure about their effects. How do they work and will they actually help you to reduce body fat? In this article, we provide an in-depth review of carb blockers, their effects on your health, and whether they really help with weight loss.

What Are Carb Blockers?

Let’s start by addressing the most fundamental question – what is a carb blocker? Sometimes known as ‘starch blockers’, they are products that prevent your system from digesting carbohydrates. They are available as dietary supplements for weight loss and prescription medicines for people with specific digestive disorders. The latter form is used to treat people with type 2 diabetes or those who have an intolerance to glucose. However, in this article, we’ll focus on the versions that are marketed as weight loss supplements.

The idea behind carb blockers is that they prevent starchy foods from being fully digested. This allows them to pass through the digestive system without being absorbed so your body doesn’t take on the calories they contain. In theory, this means that you can enjoy the taste and satisfaction of pasta, bread, and potatoes without gaining any weight. However, the reality is much more complex than this.

Ingredients in Carb Blockers

Carb blocker pills usually contain a range of ingredients with so-called weight loss benefits. The one that is thought to prevent carbs from being digested is white kidney bean extract. This compound acts as an alpha-amylase inhibitor which stops the production of key digestive enzymes. It’s recommended than 1500-3000mg of white kidney bean extract per day is needed to block carbs. One capsule will usually contain 500mg which means people take 1-2 tablets prior to each main meal throughout the day.

woman measuring waist

How Do Carb Blockers Work?

Carb blockers work by preventing digestive enzymes from being produced. Carbohydrates are made from chains of sugar that need to be broken down in order to be absorbed. A digestive enzyme called amylase is responsible for this but carb blockers prevent its production. This means that certain types of carbohydrate can pass through the digestive system without being absorbed.

Carbs come in two main forms – simple and complex. Simple carbs are made from short chains of sugar and found in foods like fruit (as fructose) and dairy products (as lactose). They are also the key macronutrient in processed foods and drinks like desserts, sweets, and soda. Complex carbs have a more complicated structure and come from bread, pasta, potatoes, and rice. Their intricate chains need to be broken apart by amylase before the sugars can be absorbed by the body.

Carb blockers prevent this from happening so that complex carbs pass through the digestive system without entering the bloodstream. In theory, this means that the calories aren’t absorbed and there’s no impact on blood sugar levels either. However, carb blockers don’t stop simple carbs from being digested.


This type of supplement is mainly associated with weight loss and dieting. The capsules are often seen as an easier alternative to healthy eating and regular exercise. The potential benefits of carb blockers include…

  • Aid weight loss – by reducing calorie intake from carbohydrates
  • Decrease appetite – possibly by affecting hormones related to hunger or slowing the rate of stomach emptying
  • Control blood sugar levels – by decreasing the sugar that is absorbed from carbs
  • Provide beneficial resistant starch – which is associated with healthier gut bacteria and lower body fat
  • Allow you to enjoy carb-rich meals – without consuming the calories
  • Remove feelings of deprivation – that are sometimes associated with dieting and make it harder
  • Simple to take – involves consuming 1-2 tablets before meals
  • Easier to stick with – as it doesn’t involve making lifestyle changes to diet or physical activity

You might be thinking that these benefits are too good to be true. The fact is, carb blockers can deliver on these beneficial aspects but that doesn’t mean they’re good for you. Any kind of ‘quick fix’ should be regarded with caution, especially when they have the potential to affect our health. As you’ll see in the next few sections, there is also plenty to be skeptical about when it comes to carb blockers.

Potential Side Effects

These types of supplement can also cause a number of unwanted side effects. When complex carbs aren’t absorbed in the usual way, they pass into the long intestine where they ferment. This can lead to gasses being released that cause cramping, bloating, diarrhea, and flatulence. These aren’t usually severe side effects but are often unpleasant enough to put people off taking the tablets long-term.

However, if you take insulin for diabetes then it’s crucial to talk to a medical professional before taking them. There’s the potential for carb blockers to result in low blood sugar levels so get advice from a doctor first.

If you do decide to try them, then it’s important to choose products from a reputable brand. Research by the FDA has shown that less than 20% of supplements contain the ingredients that they claim to. Many also include unlisted substances such as banned prescription drugs or compounds that are known to cause health issues.

It’s therefore vital that you purchase any supplements from a trusted brand and authentic supplier. The Phase 2 carb blocker is probably the most well-known brand and used as an ingredient in many different weight loss supplements.

Can Carb Blockers Help with Weight Loss?

The evidence relating to carb blockers is mixed. Some studies have shown that they do help people to lose weight whereas others do not. A few clinical trials have found that taking carb blockers resulted in 1-2.5kg (2-5.5lbs) of weight loss. They appear to have the greatest effect on people who eat a larger volume of complex carbs (probably because it blocks this type more effectively).

However, other trials have not found any difference in weight loss results which indicates that they may not be effective at all. In either case, most of the research isn’t particularly high quality since it involved a small number of participants or was conducted over a short time period.

This makes it hard to say whether the results achieved are truly representative of the large-scale public or what the effects are long-term. Likewise, carb blocker reviews from real users also reflect these mixed findings, with some achieving weight loss and others not experiencing any results.

These tablets inhibit digestive enzymes but that doesn’t automatically mean that carbohydrates won’t be absorbed. Studies have shown that carb blocker capsules prevent 50-65% of amylase enzymes from working which still leaves enough to digest carb-based foods. Another study indicated that some carb blockers are capable of inhibiting 97% of amylase enzymes yet this only stopped 7% of carbs being blocked.

It’s thought that they most likely slow down the amount of time it takes for carbohydrate to be broken down rather than stopping it altogether. If you’re eating carbs thinking you have a free pass but the pills aren’t really effective, you could actually end up gaining weight.

The other issue with these supplements is that they only block complex carbs from being absorbed. These are the ones that tend to be most satisfying since they keep you feeling fuller for longer. They don’t block simple carbs found in added sugars or processed foods. These are the more problematic type for people trying to lose weight yet aren’t influenced by taking the capsules.

Should You Take A Carb Blocker for Weight Loss?

Carb blockers may help you to lose weight if you’re someone who eats a lot of complex carbohydrates like pasta and bread. However, that doesn’t necessarily mean that you should take them. Like most quick fixes, they’re unlikely to help you keep weight off long-term. The main issue with carb blockers is that they don’t help you develop healthy lifestyle habits. Taking this type of supplement won’t support you in making dietary changes that lead to weight loss for good. Without adopting a healthy diet, as soon as you stop taking them, you’ll put the weight back on.

Effective Alternatives

Carb blockers aren’t a substitute for a healthy, well-balanced diet and shouldn’t be used as one. Adopting a healthier diet that’s rich in lean protein, fruits, and vegetables is likely to be a much more effective option long-term. Incorporating physical activity into your daily routine will help to burn off carbohydrates while enabling you to enjoy their health benefits too.

Even the best carb blocker will cease working as soon as you stop taking it. But eating healthily and exercising regularly helps to increase your metabolism. This means that your body burns more calories even when it’s not doing anything.

If you want a little help along the way, then PhenQ can be a more effective weight loss supplement. Unlike carb blockers, its use is supported by proven scientific research as well as reviews from real people. It suppresses your appetite so that you crave foods like bread, pasta, and sweet treats less. This enables you to build healthy eating habits and get used to your new diet without feeling deprived or hungry. It’s also packed with metabolism-boosting ingredients to kick-start calorie burning from day one.


Carb blockers are marketed as weight loss supplements that prevent carbohydrates from being absorbed. They stop digestive enzymes from functioning as they should so that complex carbs from bread, pasta, and rice pass through the system. However, the evidence around their effectiveness is mixed so more research is needed.

They also don’t help you to make healthy lifestyle changes and any effects that are seen will be reversed once you stop taking them. A balanced approach to food, exercise, and lifestyle habits is a more effective option long-term.