How Your Diet Affects Your GI Track

We always hear about how obesity effects your heart, blood vessels and joints. Most people have no idea how much it also effects your GI track. Let’s look at how it does.


Gastroesophageal Reflux Disease (GERD) is a very common condition effecting almost 20 percent of the population at least to some degree. It results when the sphincter at the lower end of the esophagus fails to remain closed which allows stomach contents to bubble up into the esophagus. These contents are at times very harmful to the lining of the esophagus as they are acidic. The result is that the esophagus is burned by the acid and injury results. The esophageal lining is very similar to our skin so you can imagine what spilling acid on your skin would do.

The patient with GERD usually develops heartburn when this occurs. In addition, the patient can develop symptoms that are not seemingly related to their esophagus. They can suffer with asthma, chronic cough and even sinus problems.

GERD is very definitely made worse when the patient is obese. The extra pressure that this precipitates in the abdomen increases the stress on the lower esophageal sphincter and it fails to remain closed. Obesity is definitely a risk factor for worsening GERD.

Gallbladder Disease

Obese patients are at increased risk for gallstones. We usually look upon the patients who develop gallstones as belonging to the “4F” club, they are fat, female, fertile and forty. It is very common for women who are overweight and who have had pregnancies and are middle-aged to develop gallstones. This is due to the fact that they produce bile that is saturated with cholesterol which falls out of suspension and precipitates the development of gallstones. It is estimated that 20 million Americans have gallstones and do not know they have them. About 2 percent of this population will need gallbladder surgery every year. Obesity is definitely a risk factor for gallstones.


Liver Disease

Obese patients are increasingly developing a disease of the liver due to excess deposition of fat. Fatty liver is today the most common cause of abnormal liver enzymes. This is due to the fact that the liver is the first organ that receives the output of the GI track. Since it is the “chemical plant” of our body, it receives the contents of the food we eat first. Unfortunately, much of this fat never leaves the liver and deposits there. It then causes inflammation in the liver which precipitates liver injury. This injury, if allowed to continue, can proceed to the development of cirrhosis of the liver. Obesity is definitely a cause of serious liver disease.

Altered Bowel Motility

A high fat diet has an effect on how the GI track moves. It slows it down. As a result, the stomach will empty slower. This causes it to hold on to the food for a longer period of time. If the patient then lies down or does some strenuous activity, GERD will occur.

High fat diets can slow the passage of food as it passes through the small intestine. This can result in bloating and distention. A high fat diet results in much slower colon transit. Combine this with the fact that the patient who eats a high fat diet also usually eats less fiber, and you can see that constipation will be a major problem of a high fat diet.

Altered Intestinal Bacteria

We have discussed elsewhere in this book that certain bacteria (Firmicutes) have the ability to ferment fiber into fat. This can result in as much as 500 extra calories per day as this fat is absorbed across the colon lining. So the bacteria in your colon can cause you to gain weight.

Equally interesting is the fact that patients who eat high fat diets have a higher incidence of Firmicutes in their colon. So at this time it appears that if you eat a high fat diet, you will promote the colonization of your colon with bacteria that will promote further fat intake.

As you can see, obesity greatly affects the GI tract in multiple ways. Getting weight under control is the first step to relieving the ailments described above.

Irritable Bowel Syndrome (IBS)

IBS is a condition that effects 15% of the world population and is known for its “ABCs”: abdominal pain, bloating and change in bowel habits, either constipation or diarrhea. The main theories surrounding IBS include problems with altered gut motility, abnormal sensitivity and enhanced secretion. A single cause does not exist.

Bloating and flatulence (gas) are frequent complaints in patients with IBS. It has become increasingly evident that our diet can precipitate these symptoms through the interaction of the contents of our diet with the bacteria that inhabit our GI tracts.

The foods that can cause these symptoms fall into a category known as FODMAPs, which stands for: Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols. These substances are all sugars that are poorly absorbed in some people and cause fluid to enter the intestine. Since they are not absorbed, they pass into the colon where they are fermented by the bacteria that live there.

In order to understand how these sugars cause GI symptoms, we need to review how sugars are absorbed by the intestine. As we discussed in the “C” chapter, carbohydrates are long chains and sheets of simple sugars connected by chemical bonds. We cannot absorb carbohydrates. They must first be “hydrolyzed” or broken down into simple sugars. Unfortunately some of us lack the enzymes necessary to break them down. Lactose is a perfect example (see Lactose Intolerance). There are others though who cannot break down some of the others. This leads to the movement of fluid into the intestine with its associated bloating and distention.

Even in people who can break down these carbohydrates, symptoms can still develop if they are ingested in an incorrect ratio. Table sugar (sucrose) is a disaccharide which means that it is composed of two sugar molecules connected together by a bond. The two sugars are glucose and fructose. Interestingly the cells of our small intestine can absorb sucrose very well since the transporter built into the cells that line the intestine function the best when glucose and fructose are present in equal concentrations. Unfortunately, much of our sweetened beverages are sweetened with high fructose corn syrup (HFCS).
Ingestion of HFCS causes the intestinal contents to be dominated by fructose without an equal amount of glucose. This overwhelms the transporters and causes the fructose to be malabsorbed. The unabsorbed fructose then passes into the colon where it is fermented into gas by the bacteria in the colon. Symptoms therefore develop characterized by bloating, distention, gas and diarrhea.

Foods that contain the most FODMAPs include:

  • Apples
  • Artichokes
  • Asparagus
  • Broccoli
  • Cabbage
  • Chickpeas
  • Honey
  • Mangos
  • Onions
  • Peaches
  • Pears
  • Peas
  • Watermelon
  • Wheat and Rye