Fast food fast tracks weight gain

Fast food generally means fast calories and a fast track to excess energy and weight gain, so below we outline why it’s important to slow digestion.

Better meals are low GI

If we can slow digestion and absorption of the food we eat, we can take a load off our system and reduce the chance of developing diabetes.

One way to slow digestion is to spread our meals out, allowing our body to deal with the calories in its own time.

While this works for most people, if you suddenly start eating multiple courses, particularly high-calorie courses, you can quickly put on weight. You can take an alternative approach by eating foods that deliver their nutrients at a slow pace.

We can appreciate this by considering how quickly a food causes a rise in our blood sugar, or Glycemic Index (GI). GI is a measure of the amount of calories in food and was originally developed as a food selection guide for people with diabetes.

Low-GI foods (<55) are ‘slow’ foods. They deliver their sugar load more slowly, so our sugar levels remain steadier. These foods are less likely to contribute to fat production.

High-GI foods (>70) are ‘fast’ foods that break down their sugars quickly during digestion. Refined sugars need very little digestion, resulting in a rapid rise in our blood sugar level. The foods that contain them such as soft drink and icing have a high GI.

The GI of our diet is strongly associated with our risk of heart disease, diabetes and obesity, so reducing our load by switching to low-GI foods is a simple way to reduce these risks. Low-GI foods also make us feel full and keep us satisfied and sustained for longer.

Many foods now carry the GI symbol. An improved version of the glycemic index incorporates both the GI level and the sugar quantity or Glycemic load (GL). The GL of our meal or daily diet correlates with the effort required to keep our metabolism in check, so if we keep our GL low, we also keep the work of our metabolism at manageable levels and better preserve it for the long-term.

Slow digestion by including more fiber

Another simple way to slow digestion and absorption is to include more fiber in our diet.

Fiber transforms the contents of our intestines into a gel that releases its nutrients gradually and completely. Most diets contain too little fiber because we don’t eat enough fruit and vegetables and the cereals and grains we consume are often heavily refined.

By simply replacing refined products with wholegrain equivalents, without even changing our diet, we can more than double our intake of total and soluble fiber. By mixing wholegrain products with our meal (e.g. bran with cornflakes), we can feel full sooner (thereby eating less corn flakes) and reduce our GI to more manageable levels.

Making the most of every mouthful

Many foods contain what are known as ‘empty calories’. These are calories that give us energy, but few other nutrients. Soft drinks, sweets and snacks rich in processed fats and carbohydrates (i.e. high-energy foods) are classic examples.

On the other hand, some foods are ‘nutrient-dense’ and deliver a complete nutritional package. If we want to stick to our plan of limiting calorie intake while maintaining a balanced diet, we need to reconnect nutrients with calories and substitute empty-calorie foods with nutrient-dense foods.

Fruit and vegetables, whole grains, nuts and seeds all provide substantial amounts of nutrients, known as phytonutrients, and generally fewer calories.

But it is not just plants that have nutrients. Lean meat is more nutrient dense than mince, and low-fat yoghurt is more nutrient-dense than full-cream milk. When we choose foods based on nutrient-density, we will find it’s much easier to achieve a better diet.

Tips to slow your mealtime down

  • Plan your meals in advance so you don’t have to prepare them last minute
  • Turn off the TV when you eat
  • Take the time to cook and savor a meal
  • Take 10 minutes out before you eat to relax and prepare your body for receiving nourishment – practice breathing, do a mini meditation or just involve yourself in the cooking process
  • Sit down at the table and eat with your family
  • Remember to chew and taste your food


  1. Glycemic Index Measures Show Substantial Variability. Medscape. Sep 09, 2016.

Last reviewed 31/Mar/2017

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Dr Merlin Thomas

Professor Merlin Thomas is Professor of Medicine at Melbourne’s Monash University, based in the Department of Diabetes. He is both a physician and a scientist. Merlin has a broader interest in all aspects of preventive medicine and ageing. He has published over 270 articles in many of the worlds’ leading medical journals

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