How your digestive system can cause weight gain

Disclaimer: Please note that this article is research based and some of the views and findings do not conform with the CSN Diet.

Ever wonder why you feel hungry all the time?

‘My mouth is watering’ is not just an expression, it’s quite literal. We have all experienced our mouths flooding with saliva in anticipation of our favourite food.

This saliva signals the start of the digestive process. How does food travel through your body and how does that affect weight management? 

Let’s take a journey through the organs that ensure you get the most out of your meals.

What is digestion?

Digestion refers to the process in which your body breaks down the food you eat, takes from it what you need and gets rid of the rest.

You might quickly forget about that extra slice of pizza that you allowed yourself, but your body works with it for quite some time after you enjoyed the cheesy indulgence.

The route followed by that pizza in your body starts in your mouth, from where it goes down the esophagus to the stomach. Next up is the small and the large intestines. 

It takes food around six to eight hours to get through the first parts of the process and reach the large intestines (colon). It will spend around 36 hours here, depending on the person.

how long to digest food

Factors that influence digestion time

The time it takes for food to pass through your system varies between people and circumstances:

  • Men and women aren’t equals when it comes to digestion, with men generally digesting their food faster than women.
  • Different types of food digest at different speeds. 
  • Medical problems relating to the digestive system can influence digestion time. This includes conditions like irritable bowel syndrome, Crohn’s disease and diverticulitis.  

Food’s journey through your body

Let’s take a look at what happens from the minute you set eyes on that pizza until your body discards it again.

Mouth Chewing kickstarts the process by breaking the food down into smaller pieces, and your tongue mixes it with saliva. This prepares the food to get swallowed.

The resulting soft, moist and rounded mass is called a bolus. The bolus is now headed to your esophagus.

Esophagus The esophagus is a pipe that leads food from your mouth to your stomach. This happens through an interesting process called peristalsis.

The food (bolus) enters the esophagus. Muscles behind the bolus the contracts, while the muscles in front of the bolus relax. This forces the food down the esophagus, towards the stomach.

At the end of the esophagus we find a muscular valve called the lower esophageal sphincter. This acts as a little doorway that allows food into the stomach.

If the sphincter doesn’t close off properly after letting food pass through into the stomach, food or stomach acid can find their way back into the esophagus, leaving you reaching for the antacids.

Stomach This is where the real action starts. The stomach is lined with glands that secrete acid and enzymes. These continue to break down the food.

The stomach muscles further mix up the food. By now your pizza has turned into a thick and creamy liquid known as chyme. 

Similar to what happens in the esophagus, muscle movements propel the chyme into the small intestine. 

It once again moves through a valve, called the pylorus. Only about 4mm of chyme moves through the pylorus at a time. The rest continues to mix in the stomach.

Small intestine In the first part of the small intestine the pancreas, liver and gallbladder starts doing their work. 

The breakdown of proteins, carbohydrates and fats is the responsibility of the pancreas. This happens via enzymes that the pancreas produce.

The liver creates bile, which further aids in the breakdown of fats. After this process of properly breaking down the food, it moves further down the small intestine.

Now it’s time to extract the nutrition we need from our food. The food gets broken down into molecules of the various nutrients present in the food. 

These nutrients then move through the walls of your small intestine, go into your bloodstream and travel with your blood to the parts of the body where it is needed.

Large intestine Whatever cannot be used by the body is waste. This moves through the large intestine where any water that forms part of the waste material gets absorbed.

A soft substance called stool has now formed. Stool gets pushed into your lower large intestine and rectum. Doing so stretches the rectal wall, alerting its owner to get rid of the waste with a bowel movement.

Link between digestion and weight loss

Weight loss is a challenge for mostly one reason: you get hungry. How often you get hungry has a lot to do though with the rate at which different types of food digest.

Being aware of this helps you to make informed choices about what you choose to eat, as the right choices will help you to feel fuller for longer, reducing the need to overeat.

Here’s the kicker: the foods that we like to grab to sort out an unexpected growling tummy during the day, are exactly the type of foods that break down quickly, leaving us hungry again.

A few examples of wrong food choices that will leave you wanting more include:

Low fat yoghurt Many of us view this as an obvious healthy choice. We get fooled by the words ‘low fat’. Sure, the fat content may be low, but did you check the ingredients list?

Low fat yoghurt typically contains large amounts of sugar, which is easily broken down by the body. You stay hungry and end up consuming large amounts of empty calories.

The same is true for salad dressings that are labelled ‘low fat’. Sadly, the sugar is still present in your seemingly guilt-free bottle.

Muffins, croissants, fruit juice, many breakfast cereals and pies All of these sometimes feel like reasonable choices, but they are loaded with sugar. Yes, even savoury food can contain sugar.

The body wastes no time breaking sugar down as glucose, resulting in the body releasing more insulin. Too much insulin reaching the cells can cause low blood pressure. 

Egg whites Be careful of avoiding egg yolks to lose weight. The yolks contain the goodness that keeps you fuller for longer.

White bread, white pasta, white rice These do not contain natural fibrous grains that aids in keeping you fuller for longer.

What you want is food that digest slower, keeping you fuller for longer. You want fibre. Another healthy option is food with a high water content, as it makes you feel full without the calories.

A few healthy options that fills you up include:

  • Replacing that fat free yoghurt with full fat plain or Greek yoghurt. Add some nuts and berries for nutrition, texture and flavour.
  • Avocados are both delicious and healthy.
  • Oatmeal is better than a sugary cereal that will not last you a very long time after breakfast.
  • You can never go wrong with fresh fruit and vegetables. You will quickly get used to the refreshing taste of a raw, crunchy carrot, just hang in there.

Healthy gut, happy you

Compiling an eating plan that both keeps you healthy, full and satisfied, and allows you to reach your weight goals is a fine balancing act.

A reputable dietician will keep matters of the digestive system in mind along with all the other factors that play a role in healthy weight management.

Being healthy equals feeling good, and that is always worth the effort.



Hi, my name is Karien Nel and today I’m 37kg lighter than the day I started my weight loss journey with CSN Diet.

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