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Good vs Bad Carbs – What’s The Best Carbs for Weight Loss?

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The argument around good and bad carbs is one that has been going on for years, so here’s the science and unbiased truth.

Some say all carbs are bad, some say only certain types are bad and some say it really doesn’t matter; so what’s the truth?

The big thing is, if you fall on the side of carbs being okay to consume, the goodness or badness of the carbohydrates you consume is largely dependent on your body’s ability to process them, as well as the body’s need for them.

As with almost any topic in exercise and nutrition, the answer to this age-old question is largely based on the context in which the carbohydrates are being consumed, rather than simply one being good and one being bad.

In this article, I’ll discuss some science-based perspectives on whether there are actually ‘good’ and ‘bad’ carbohydrates and how this information can be applied to your own life.

Carbohydrates 101 – A Quick Overview

Chances are, you’ve heard many different terms associated with carbohydrates, ranging from simple and complex, to whole and refined. But what’s it all mean?

Before getting into the terminology, you first need to understand what carbohydrates are and what their purpose is in the human body.

Carbohydrates are made up of different elements, specifically carbon, hydrogen and oxygen. In its simplest form, these atoms can bind together to form what is called a monosaccharide. This is otherwise known as a simple sugar (1).

However, as these monosaccharides begin to chain to other monosaccharides, they can create disaccharides (meaning two) or polysaccharides (meaning many).

As you go up the chain to polysaccharides, these are typically what are considered fiber such as cellulose, which is found in plants. In the case of fiber, the human body itself cannot digest it because we don’t have the enzymes to break it down into glucose.

However, the bacteria in our gut can do this, which is one of the reasons you may experience excess gas from eating fiber (the bacteria ferment the fiber, creating gas).

The other types of carbohydrates are already either mono or break down to the carbohydrate’s simplest form, which is known as glucose. This is one of the main ways that the body receives and uses energy.

What Happens When You Consume Carbohydrates?

After you ingest carbohydrates and they reach your stomach, these carbohydrates begin to breakdown into smaller versions of themselves until they reach glucose, which is the smallest version of carbohydrate.

This is where the idea of simple and complex carbohydrate comes into play.

Simple carbohydrates such as pure sugar are considered monosaccharides and cannot be broken down any further. As such, they very quickly enter the bloodstream (2).

Complex carbohydrates, which are often found in things like whole grains and vegetables, have long chains of monosaccharides bound together. In the stomach, they are then broken down all the way to glucose. It is the length of this chain that makes them “complex” and slower to digest and reach the bloodstream (2).

So as you can see, all carbohydrates (apart from indigestible fiber) are broken down into glucose (sugar). It’s only the length of the chain that determines how quickly this occurs and reaches the bloodstream.

Once glucose enters the bloodstream, a peptide hormone called insulin is secreted from the pancreas, which drives this glucose out of the blood and into various blood tissues such as fat and muscle tissue (3).

Insulin Response To Carbohydrate

Insulin is known as the devil, which is probably the first mistake that anti-carb or low carb gurus make.

The insulin response to ingested carbohydrate is a primary culprit behind why many people regard some carbohydrates as good and others as bad. Basically, they make a judgement due to the rate at which they are broken down and thus introduced into the bloodstream.

As mentioned, when sugar or glucose is in the bloodstream, insulin rises to shuttle the blood into various tissues. However, the quicker the glucose enters the bloodstream, the faster and larger the insulin response.

Unfortunately, large spikes in insulin often have potential to eventually cause a disorder called insulin resistance, where insulin can no longer effectively remove glucose from the blood (4).

This can lead to issues such as obesity and even type 2 diabetes (4, 5).  So, while it makes sense to class carbs as bad if they cause large spikes in insulin, this is really only considering one variable and in some circumstances (such as post workout), this spike is actually beneficial.


So Avoid Simple Carbs And Opt For Complex Carbs?

In short, sometimes yes and sometimes no. But as always, it really depends…

The fact is, consumption of simple carbohydrates may be fine for one person (i.e. a lean athlete), but terrible for another (a sedentary obese individual). Use or removal of the different types of carbohydrates should be a largely individual practice.

That being said, it’s always wise to err on the side of caution and use each type of carbohydrate appropriately. For example, if you are an athlete or otherwise very active, then using a simple carbohydrate might actually be advantageous for your goals when used and timed strategically.

By consuming a fast-digesting carbohydrate, you can ensure that your muscle is saturated with energy quickly, so that it can perform at your peak ability. This is even more important for individuals who have to perform multiple times in quick succession.

Additionally, simple carbs that spike insulin can often be absorbed better and aid in recovery. Due to the spike in insulin, the amino acids can also be absorbed more efficiently and so enhance muscle protein synthesis.

On the other hand, if you lead a fairly sedentary lifestyle such as an office job, then the use of simple carbohydrates when sat at your desk all day may be doing you more harm than good over the long term.

In this instance, you would likely be much better off using a slower digesting carbohydrate source, for example from vegetables, to avoid large and drastic increases in insulin and excess calorie/carb consumption (remember, simple carbs are often more calorie dense, with the exception of fruit).

Carbohydrate Amount Or The Glycemic Load Also Matters

Arguably even more important than the type of carbohydrate is the notion of consuming the carbohydrates you need.

Keep in mind that carbohydrates themselves will likely only contribute to weight gain if you consume more than is required by the body for energy purposes. When you consume calories in excess of what your body requires, you’ll gain weight, regardless of the carbohydrate type (6).

This ultimately comes down to both calorie density and total carb intake, and thus total calorie intake. In most cases, the typical sugary ‘bad’ carbs are going to have a higher level of calories and calorie density which may not make them optimal for fat loss or those needing to focus on weight loss.

In contrast, for athletes, bodybuilders or underweight individuals who can’t gain weight it would, of course, make them useful.

As you can see, it is context-dependent on you, your goals and their function at that point in time etc.

Even for the same individual, there may be a time and a place for both good and bad carbs. For example, you may focus on low calorie dense ‘good’ carbs during the day when you are less active at work.

But, later that day, you may focus on ‘bad’ carbs around the workout (before/after) as they are easier to digest and provide more simple sugars and a larger insulin response (remember, insulin is an anabolic hormone).

So, Good vs. Bad Carbs – What’s Best?

If you have fully understood this article, then you should now hopefully see that it really depends.

Obviously for the general person, (bearing in mind over 50% are overweight), and general health ‘good’ carbs should be used the majority of the time.

But realistically speaking, there aren’t clear cut good or bad carbohydrates per se, but rather, based on the context, different types can promote a reaction and provide both benefits and negatives depending on how they are used.

Remember, the speed at which a carbohydrate is broken down into glucose and enters the bloodstream plays a role in how our bodies metabolize it.

By using your physical activity level to gauge which type of carbohydrate to consume and how much of it you need, you can optimize your body’s response and avoid potentially negative outcomes.

The other key factor is the total amount of carbs a piece of food provides. In my opinion with regard to weight loss, ‘good’ carbs are those with a low energy density and lots of fiber, such as fruit, vegetables and whole grains.

Lastly, keep in mind that while carbohydrates can lead to weight gain, they aren’t directly responsible for it. It’s only when you over-consume them, relative to the energy needs of your body, that they become an issue.

This means you can still consume and enjoy both ‘good’ and ‘bad’ carbs in moderation, but just be aware of what they do, when to use them and the amount of calories and calorie density each provides.


  1. Simple vs Complex Carbs. (n.d.). Retrieved June 21, 2017, from http://www.diabetes.co.uk/nutrition/simple-carbs-vs-complex-carbs.html
  2. Crapo, P. A., Reaven, G., & Olefsky, J. (1976). Plasma glucose and insulin responses to orally administered simple and complex carbohydrates. Diabetes, 25(9), 741-747.
  3. Ludwig, D. S., Majzoub, J. A., Al-Zahrani, A., Dallal, G. E., Blanco, I., & Roberts, S. B. (1999). High glycemic index foods, overeating, and obesity. Pediatrics, 103(3), e26-e26.
  4. Reaven, G. M. (1988). Role of insulin resistance in human disease. Diabetes, 37(12), 1595-1607.
  5. Greenwood, D. C., Threapleton, D. E., Evans, C. E., Cleghorn, C. L., Nykjaer, C., Woodhead, C., & Burley, V. J. (2013). Glycemic index, glycemic load, carbohydrates, and type 2 diabetes. Diabetes Care, 36(12), 4166-4171.
  6. Spiegelman, B. M., & Flier, J. S. (2001). Obesity and the regulation of energy balance. Cell, 104(4), 531-543.

About the author

Rudy Mawer, MSc, CISSN

Rudy has a 1st class BSc in Exercise, Nutrition & Health and a Masters in Exercise & Nutrition Science from the University of Tampa. Rudy currently works as a Human Performance Researcher, Sports Nutritionist and Physique Coach. Over 7 years he has helped over 500 people around the world achieve long last physique transformations.

He now works closely with a variety of professional athletes and teams, including the NBA, USA Athletics, World Triathlon Gold Medalists, Hollywood Celebrities and IFBB Pro Bodybuilders. If you would like to get in contact or work with Rudy please contact him on social media.

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