Petra Scott holding a green smoothieIf you’ve ever tried to lose weight, you’ve probably come across the advice to cut carbohydrates out of your diet. Well, I’m here to tell you that there are some carbohydrates you definitely want to keep around. Carbohydrates have gotten a bad reputation in recent years – and it’s somewhat undeserved. In fact, rather than being a weight loss wrecker, some carbohydrates are your best friend.

In this article you’ll find out that eating the right kind of carbohydrates can actually help you get and stay slim.

Carbohydrates – The Basics

Carbohydrates are a type of macro-nutrient found in plant-based food. They provide four calories per gram and are your body’s primary source of energy. The three main forms of carbohydrates are sugar, starch, and fiber.

  • Sugar is a simple carbohydrate because it only consists of one sugar molecule (glucose, fructose, and galactose) or two sugar molecules (sucrose, maltose, and lactose). Simple carbohydrates are a great source of energy because of their simple molecular structure, often leading to a rapid rise in blood sugar (glucose) levels. Sugars occur naturally in fruits, vegetables, milk, and milk products.
  • Starch is a complex carbohydrate because it consists of multiple sugar molecules. So really, there are only two types of carbohydrates because starch is just a long chain of sugars. Naturally, then, starch has a similar effect on blood glucose levels as simple sugars. Starch occurs naturally in vegetables, grains, and legumes.
  • Fiber is also a complex carbohydrate, but as opposed to sugar and starch, it can’t be digested by humans. Instead, it passes through the intestines and is excreted in the form of feces. Fiber doesn’t provide any energy/calories and slows down the absorption of sugar/starch. The two main types of fiber are soluble and insoluble. Fiber occurs naturally in fruits, vegetables, grains, and legumes. (1)

Do Carbohydrates Cause Weight Gain?

It depends. But the short answer is no. Carbohydrates do not cause weight gain. What causes weight gain is the inability to effectively metabolize carbohydrates.

Your body can’t absorb anything larger than glucose. Therefore, both sugars and starches are broken down into single molecules of glucose. Once broken down, they enter the blood stream and increase blood glucose levels. To help transport that glucose somewhere more useful, your pancreas secretes insulin.

The first destination of choice is the brain, followed by the the muscle tissue and the liver. These organs only need so much glucose though. When your body has more glucose than it can use, insulin prompts fat cells take in all the excess glucose and store it as fat. (2) So even in healthy people, insulin functions as a fat-storing hormone.


However, this doesn’t mean that insulin makes you fat. It’s just a hormone doing its job – maintaining steady and safe glucose levels. The more steady your blood glucose levels, the less insulin your pancreas needs to release. Therefore, one piece of the weight loss puzzle is to limit carbohydrates that cause rapid blood glucose and insulin spikes. The truth is people lose weight equally well on both low-carbohydrate and high-carbohydrate diets. (3) The difference is the type of carbohydrate they eat.

Simple versus Complex Doesn’t Cut It

In the past, simple carbohydrates used to be labeled as “bad” and complex carbohydrates as “good”. The reasoning was straightforward. The “simpler” the structure, the less time it takes to digest, leading to a fast increase in blood glucose. Similarly, the more “complex” the structure, the longer it takes to digest, leading to a much smaller increase in blood glucose levels. (4)

However, this assumption turned out to be too simplistic. While certain complex carbohydrates cause rapid spikes in blood glucose levels, some simple carbohydrates don’t have much effect on blood glucose levels at all. (5) In fact, starchy foods like potatoes or white bread cause even higher spikes in blood glucose levels and insulin than table sugar (sucrose) or honey. That’s because biochemically speaking both sugars and starches are broken down into their simplest form (glucose) in the intestines and absorbed rapidly into the bloodstream afterwards. (6) Subsequently, they also cause the same glycemic (blood glucose) response and insulin release.

Petra Scott drinking a green smoothie

Glycemic Index: The Quality of a Carbohydrate

To rank carbohydrates based on their effect on blood glucose levels, scientists developed the glycemic index (GI). (4) Glycemic index compares carbohydrates one a scale from 0 to 100 according to the extent they raise blood glucose levels after eating. (4) Pure sugar (glucose) serves as a reference with a glycemic index of 100.

The glycemic index essentially represents the quality of a carbohydrate. Carbohydrates that are digested slowly have a low glycemic index (GI ≤ 55). Carbohydrates that are digested quickly have a high glycemic index (GI ≥ 70). Anything in between has a medium glycemic index (56 ≤ GI ≤ 69). (7)

The glycemic index was originally developed for diabetics. However, athletes, bodybuilder, and health conscious people quickly embraced it as well. The glycemic index allowed them to control their blood glucose levels, leading to reduced hunger and cravings, balanced energy levels, and prevention of health conditions associated with frequent spikes in blood sugar, such as diabetes and heart disease. (8, 9, 10, 11, 12, 13, 14)

Limitations of the Glycemic Index

One limitation of the glycemic index is that it doesn’t account for how much carbohydrate a particular food contains. It only reflects how quickly the carbohydrate-containing food is absorbed into the blood. (15)

Take beets or carrots, for example. The sugar in beets and carrots is rapidly absorbed into the bloodstream. Therefore, both beets and carrots rank pretty high on the glycemic index scale (64 and 73 retrospectively). However, to understand a food’s complete effect on blood sugar, you need to know both how quickly the sugar is absorbed into the blood (= the quality of a carbohydrate) AND how much sugar the food actually contains (the quantity of a carbohydrate). That’s where the glycemic load (GL) comes in.

Glycemic Load: The Quality AND Quantity of a Carbohydrate

The glycemic load describes both the quality AND the quantity of a carbohydrate. It’s calculated by multiplying the food’s glycemic index by its carbohydrate content measured in grams, and divided by 100. For a typical serving, glycemic load of 10 or under is low, 11 to 19 is medium, and 20 or more is high. (7)

Going back to our example with beets and carrots, while the sugar from those vegetables is absorbed rather quickly (= high glycemic index), there’s not a lot of sugar to begin with (= low glycemic load). The glycemic load of 1 raw beet is 3 and that of 1 raw carrot is 2. This explains why despite beets and carrots scoring high on the glycemic index, you’re not likely to gain weight eating them.

Limitations of the Glycemic Load

Unfortunately, human nutrition is incredibly complex. While more useful when it comes to weight loss, glycemic load is not the be-all end-all tool either. Here’s why:

1. Glycemic Response to the Same Food Varies from Person to Person

Scientists determine glycemic index values experimentally. Essentially, they feed 10 or more healthy people 50 grams of digestible carbohydrate and then measure the effect on their blood glucose levels over the next two hours. The final glycemic index value for the test food is the average glycemic index for the 10 people. (16)

The difficulty is that two people can eat the same carbohydrate in the same quantity and have considerably different blood glucose response. (17) Making matters even more complex, great variation in glycemic response occurs not only between people, but also in a single individual from day to day (18). Variables such as the extent of chewing food prior to its swallowing (19) or the individual’s rate and extent of digestion and absorption all affect glycemic index values. (20)

2. Glycemic Index Values Vary for the Same Food

This variation may reflect both different testing methods (including the use of different types of blood samples, different experimental time periods, and different portions of foods) and true differences in the characteristics of the foods (the kind of food, its ripeness, storage time, cooking method, and its variety). (5)

Using carrots as an example, published glycemic index values list carrots as having a mean glycemic index of 92, 49, and 32. (5) Potatoes are another case in point with glycemic index values ranging from 56 to 94. (21)

3. Glycemic Index Values of a Mixed Meal Are Inaccurate

Glycemic index values are only available for individual foods. Obviously, that rarely happens. Do you ever just eat plain rice? I thought so. The problem is that summing glycemic indexes of individual foods to calculate the glycemic index of a meal isn’t reliable. (22)

Adding protein, fat, and other various nutrients significantly reduce the glycemic index of a carbohydrate-containing meal. (23, 24) However, there’s insufficient information to accurately predict the effect of different combinations of foods. In fact, one study found that the formula for calculating glycemic index of a meal produces inaccurate results by up to 50%! (25)

4. Low Glycemic Index Doesn’t Equal Healthy

Glycemic index values are not the best representation of what you should be eating. There are many foods that fall into the low glycemic index category, yet aren’t healthy. One serving of ice cream (66 grams), for instance, has a glycemic load of only 8. A number that places ice cream much lower on the glycemic index scale than a serving of oatmeal. While high in sugar, ice cream is also high in fat, which lowers glycemic index values.

Criteria for Choosing Carbohydrates

Minimally processed, high-fiber, high-water, hypoallergenic carbohydrates are the best choice for weight loss.

1. Minimally Processed 

Refined and processed carbohydrates, such as white bread, white rice, white pasta, pastries, cakes, sweets, breakfast cereals, and fruit-juices, tend to be the worst carbohydrate-containing foods for weight loss. Not only do they lack most fiber, vitamins, and minerals, but their water content is also very low. What’s left is pretty much just a rapidly digested sugar/starch.

Eating refined carbohydrates leads to weight gain (15), overeating (26), hunger in only about one hour after eating (27, 28), and cravings for more refined carbohydrates. (4) Last but not least, refined carbohydrates also increase the risk of many diseases including heart disease, type 2 diabetes, stroke, high blood pressure, colon cancer, and digestive problems. (29, 30, 31)

Whenever you have the option, choose carbohydrates coming from whole foods rather than processed ones.

2. High in Water and High in Fiber

While many whole, unrefined, carbohydrates, such as starchy vegetables, whole grains, or legumes are healthy, some of them are not your best choice if you want to lose weight.

Fiber to Sugar/Starch Ratio

For weight loss, the best carbohydrates are those with the highest amount of fiber relative to the amount of sugar/starch. Fiber is important because it slows down the absorption of sugar/starch into the bloodstream and blunts insulin response. However, too much sugar/starch is just not helpful for weight loss period. Your body still has to deal with all the sugar/starch in the blood.

As Dr. Jade Teta states, “if you really want to maximize fat loss and minimize fat storing, then you should seek out carbohydrates that have the smallest amount of sugar/starch and the highest amount of fiber”. (32) It’s the relative amount of fiber to sugar/starch rather than the total amount of fiber that counts.

Foods with the highest amount of fiber to sugar/starch are non-starchy vegetables and less sweet fruit. Starchy and sweet carbohydrates coming from whole foods, such as whole grains, legumes, starchy vegetables, and sweet fruits, might be healthy, but just not that great for weight loss. This might be confusing because you’ve probably heard that whole grains and legumes are high in fiber, which is true. However, compared to fruits and vegetables, they have less relative fiber to sugar/starch.


The second thing to consider is water. Water, same as fiber, provides bulk and promotes the feeling of fullness for longer. In fact, fiber and water are synergistic together. The soluble type of fiber absorbs water and forms a kind of gel inside your intestines, slowing down the absorption of sugars into the bloodstream. This, once again, means lower insulin levels and less fat storage.

Foods with the highest amount of water are fruits and non-starchy vegetables. On the contrary, whole grains, legumes, and starchy vegetables have much lower water content.

3. Hypoallergenic

The last consideration is the allergy-producing potential of a carbohydrate. Grains and beans usually contain some amount of gluten (a protein found in wheat, barley, rye, and all their hybrids) or lectins (proteins present in all foods, but especially grains and legumes), which can disrupt the ability to burn fat.

If you do decide to have starchy carbohydrates, choose the most hypoallergenic ones first. This includes:

  • (Pseudo)grains: amaranth, brown rice, buckwheat, oats, and quinoa;
  • Legumes: beans, chickpeas, lentils, and peas;
  • Vegetables: potatoes, pumpkin, squash, yam

Best Carbohydrate Choices

Carbohydrates that fit all of the above criteria are non-starchy vegetables and less sweet fruit.  You can eat those foods in unlimited amounts. You can still eat grains, legumes, starchy vegetables, and sweet fruit, but if your primary goal is weight loss, watch the amount you eat more closely.

Also, there are some foods that don’t contain very much fiber or water, such as garlic, shallots, or onions, but you don’t have to worry too much about incorporating them in your meals. If you’re like most people, you probably use them more as a spice than the main ingredient. And the truth is that these foods are a great choice for spicing up a meal without adding too many calories.

Here is a food chart with the most common carbohydrates (vegetables, fruit, grains, and legumes). It’s color-coded based on the amount of fiber and water the individual food contains. You can print it and put it on your fridge or just refer to it when you need to.