Do Carbs Cause Weight Gain?

MYTH VS. REALITY

While carbs are often demonised in the media, carbohydrates like any macronutrient only cause weight gain if over consumed. Sugar is a carbohydrate, and while it still only contains 4kcal per gram it often comes in forms very easy to over consume, i.e sugary drinks, sweets or cakes.

Diets high in these foods tend to be associated with weight gain because an overconsumption of sugar/carbs leads to an over consumption of calories, which leads to a calorie surplus. The calorie surplus causes the weight gain.

On the other hand a diet that is calorie appropriate will not lead to weight gain even if sugar is present in the diet. Equally, a diet that creates a calorie deficit will still lead to weight loss, even if sugar is present (2).

However, the key is managing a diet that is:

• Calorie appropriate for the goal.

• Contains enough protein and fats.

• Contains enough nutrient quality, i.e micronutrients and fibre etc.

If all three of these things are met, then having a small sugary snack in the day is not going to prevent you reaching your goal, as long as it's accounted for within appropriate calorie intake overall. In some cases you may even find including a ‘little of what you like’ each day is a sensible way of managing cravings and avoiding binges at the weekend.

This is why in my quick start guides you’ll find that some sugary snacks are available as part of your snack window, while the rest of the diet focuses on high quality, high protein, nutrient dense food.

INSULIN AND WEIGHT GAIN?

The carbohydrate-insulin model of obesity is a proposed theory that elevated insulin levels cause storage of body fat and obesity rather than over-consumption of calories. As carbohydrates, particularly sugars, are the main drives of insulin elevation carbohydrates are often demonised as causing fat gain.

This theory is not currently supported by the scientific literature, and several studies have demonstrated that diets high in carbohydrates do not cause more weight gain that diets high in fats when calories and protein are the same in both diets (3),(4). This was the case even though the high carbohydrates groups did show higher insulin levels. 

Insulin is an essential hormone which draws glucose (sugar) into the muscles and liver for use as fuel. It does play a role in fat storage and fat breakdown alongside many other essential hormones. Looking at individual functions of different hormones within the body without an overall context in mind can be misleading. 

Overall energy balance of calorie intake versus calorie expenditure determines changes in total body weight, while factors such as protein intake, nutrient quality, training and recovery will also determine changes in body composition such as muscle and fat ratios (5). 

REFERENCES:

(1) Holesh and Bhimji (2017)
(2) Morenga et al. (2013)
(3) Hall (2016)
(4) Hall (2015)
(5) Aragon et al. (2017)