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Why Carbohydrates Don’t Need To Lead To Weight Gain

Holly Lehmann is a Registered Associate Nutritionist specializing in weight loss and behavior change. She is the founder of Eat Better with Holly that offers a unique and personalized weight loss programmed, 'Eat Better Feel Better.'

Executive Contributor Holly Lehmann

Carbohydrates (carbs) often have a bad reputation amongst dieters. They are easily demonised and perceived as the reason for weight gain. Carbs are usually associated with bread, pizza, and pasta, but carbs are much more than this. Vegetables contain carbohydrates, and so does natural yogurt! The milk sugar (lactose) in yoghurt is a type of carbohydrate. It can be overwhelming! That’s why I want to clarify what exactly carbohydrates are, to help dieters make favourable dietary choices without restricting important nutrients. There is also a simple explanation as to why carbs can lead to weight gain. Let’s take a look!

 Closeup photo of breads in basket.

Why do carbs have a bad reputation?

Carbohydrates get broken down into glucose when eaten. Glucose then enters the bloodstream and gets distributed to cells to be used as energy. Once cells have received the glucose they need, any extra glucose is stored in our body as glycogen in the liver and muscle cells. Here’s the thing: stores can get full! Our body can only store approximately 500 grams of glycogen; around 100 grams in the liver and 400 grams in muscle. ¹ So, what happens to the glucose that can’t be stored? Any excess glucose is converted into fatty acids and stored as fat in adipose tissue. This process is known as de novo lipogenesis. ² This is why, when consumed in large amounts exceeding daily calorie needs, carbohydrates can lead to weight gain. In today’s Western society, it can be easy to overconsume carbs because they tend to be everywhere (e.g. breakfast cereals, pastries, cakes, white bread, burger buns, crackers, tortillas, biscuits, sweets…)

What exactly are carbohydrates?

Carbohydrates can be broken down into three groups: sugars, starches, and fiber.

1. Sugars

Sugars are also known as simple carbohydrates. These sugars are found naturally in fruit, vegetables and milk, such as; glucose, fructose, lactose.

There is a distinctive subcategory called, “free sugars.” Free sugars are the sugars we should minimize. Free sugars get broken down into glucose extremely quickly and include:

  • Honey

  • Any sugars added to food and drink by manufacturers

  • Natural occurring sugars in fruit juices and smoothies

What is meant with the last point? The natural sugar in a whole piece of fruit e.g. in an orange, is not a free sugar. This is because the natural sugar is combined with fiber within the fruit and is therefore released more slowly into the blood stream compared to orange juice. When a whole piece of fruit or vegetable is pressed, the natural sugar immediately turns into free sugar because the fiber has been removed and basically left behind. It’s recommended that we consume no more than 30 grams of free sugars per day, this is around 7 teaspoons. ³ It can be easy to think of white table sugar as the usual type of sugar added to products, however, free sugars can be in disguise! On packaging, look out for words such as: high fructose corn syrup, fruit juice concentrate, honey, maple syrup, treacle, molasses, agave syrup, dextrose, sucrose, maltose, cane sugar, nectars. These are all free sugars.

2. Starches

Starches are known as complex carbohydrates. They take longer for our body to digest because their complex structure needs to be broken down first. They release energy more slowly and, therefore, tend to lead to a slower rise in blood sugar levels compared to simple carbohydrates. They can be good sources of vitamin B1, iron, calcium and folate.  Starchy carbohydrates include e.g. potatoes with skins, wholegrains, chickpeas.

3. Fiber

Fiber is also a complex carbohydrate. It is also known as roughage and is found in fruit, vegetables and starchy carbohydrates. Our body doesn’t have the necessary enzymes to digest fiber and so it’s not used as energy. Instead, it has many other beneficial functions, especially on gut health, contributing to gut microbial diversity and providing bulk to stool to support regular bowel movements and reduce constipation.

Carbs provide us with energy enabling us to feel active throughout the day. Glucose (the building block of carbohydrates) is the only sugar that can cross the blood-brain barrier. Our brain needs around 130 grams of glucose per day.

Healthy vs. unhealthy carbohydrates

Let’s start with the “un-healthier” versions. These are known as refined carbohydrates. Refined means they have been processed; products with lots of added sugar or grains that have had their outer bran and germ removed (e.g. white bread, white rice..). Overall, these types of carbohydrates have fewer nutrients, less fiber and are usually less filling. It’s not to say one cannot enjoy them in small amounts though!

The “healthier” versions are the opposite; products with minimal or no free sugars, fruit, vegetables, legumes and wholegrain foods. A systematic review by Aune et al. suggests consuming 90 grams (3 servings) of wholegrains per day may reduce the risk of cardiovascular disease by 22%.  Also, these foods tend to lead to a lower rise in blood glucose levels.

The insulin response explained

Refined carbohydrates are broken down quickly by the body due to their simple structure, which is why they usually lead to a quicker rise in blood glucose levels than more complex carbohydrates. For some individuals, a quick rise in blood glucose levels can lead to a glucose spike followed by a blood sugar drop. This can result in hunger and cravings.

When blood glucose levels rise after consuming carbohydrates, insulin is released by the pancreas. The role of insulin is to remove glucose from the blood and into cells, for the cells to use glucose as energy. Therefore, consuming a lot of refined carbohydrates over the day, especially when snacking, can lead to a consistent need of insulin. The higher the sugar content of a food, the more insulin that is produced. Here’s the thing! Insulin temporarily halts the breakdown of fat. This is because its role is to help provide energy to cells and not help the cells release energy. Insulin inhibits the enzyme lipase, which is responsible for breaking down fat. For dieters, it’s therefore beneficial to try and keep insulin levels steady by consuming more complex carbs.

How many carbs should I eat in a day?

There is no one-size-fits-all. Some individuals feel more well eating less carbohydrate rich foods whereas others feel better with more. It also depends on age, gender, overall health and activity levels. Overall though, it is recommended that carbohydrates contribute to 50% of our daily energy intake.  This is around 250 grams for a 2,000 daily calorie intake.

Carbohydrates is a complex topic and this was only a brief overview that has hopefully clarified any questions or thoughts you may have had. In summary, consuming large amounts of refined carbohydrates can lead to weight gain because excess glucose is stored as fat. Complex carbohydrates are usually much more filling and tend to lead to a smaller insulin response. It may feel overwhelming to know what to buy and what to leave on the shelf as nowadays there is so much choice in food! This is where I’m here to help as a qualified Nutritionist. I run a weight loss and behaviour change programme, where I make losing weight fun and help you turn healthy eating into a lifestyle change!

A discovery call can be arranged with me; click here, where you can find detailed information about the programme ‘Eat Better Feel Better.’

Follow Holly on her Facebook, Instagram, and LinkedIn or visit her website for more info!

Read more from Holly Lehmann


Holly Lehmann, Nutritionist

Holly Lehmann, Registered Associate Nutritionist, is passionate about helping others optimise their diet and lifestyle to lose weight, maintain weight loss and feel healthier and happier overall. Before changing career to become a qualified Nutritionist, Holly worked in management positions in the luxury hotel sector for around 10 years. She is fully aware of how shift-work and long-working hours may lead to poor dietary habits. Her personalised weight loss programme, 'Eat Better Feel Better' is tailored to each individual client, taking their lifestyle into consideration and supporting them in changing any poor dietary habits into long-lasting, beneficial ones.



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