Health · Wellness

Does your stomach actually shrink when you diet?

Does your stomach actually shrink when you diet? Can your stomach stretch if you consistently overeat?

Contrary to popular thought, people do not have a larger or smaller stomach than the person next to them. As you grow into an adult, your stomach will grow with you. However, once you reach adulthood, your stomach stops growing and pretty well stays the same size.

Thinking that your stomach shrinks in size when you eat less is actually a myth. Your stomach expands and contracts as you eat and digest the food but the actual size of your stomach does not change overall. However, you can reset your appetite to lower levels.  Regardless of your weight, the organs on the inside all look approximately the same. Unless someone has received surgery to shrink their stomach, a 100lb person will have approximately the same size stomach as a 200lb person.(1)

When it is empty, your stomach volume is actually less than a cup. As you start to eat, your stomach muscle relaxes to make room for the food and can actually expand 5 times larger than its empty size. On the other side, some people suffer from functional dyspepsia which is when your stomach lining is more stiff than usual and cannot fully relax – this leads people to feel discomfort even from a small amount of food – which some people may think means their stomach is smaller, which isn’t the case. (2)

So why do we get hungry? Why can some people eat more than others if all of our stomachs are the same?

Our bodies get the feeling of hunger when we’ve used up all the food we’ve eaten as energy and our insulin and blood sugar drops. The hormone connected to the appetite, ghrelin, then lets us know its time to eat.

Recent studies from Aberdeen University suggest that the brain cells vital to regulating appetite slow down as we get older, leading to weight gain. (3) This means that as we get older it takes us longer to feel full so we then tend to eat more.

A study conducted by Robert Lustig, professor of clinical paediatrics at the University of California, suggests that sugar plays an important role in overeating. When you’ve had enough to eat, your fat cells send leptin to the brain to let you know it’s time to stop eating. However, as you eat more sugar, it starts interfering with this process. When you consume a diet high in sugar, this leads to insulin resistance, which then can lead to leptin resistance. (4) So, a diet high in sugar will start playing tricks on your body and when your body creates a leptin resistance, it will think you are constantly starving or hungry, meanwhile you’ve just eaten, and should feel full.

Here are two other reasons why you may be eating more than you should:

  • If you are sleep deprived you tend to eat more because the ghrelin hormone levels are higher when we lack sleep
  • Menopause can make you more hungry thanks to the fluctuating levels of progesterone. Higher levels of progesterone increases the need for energy, therefore making you crave food

Changing your appetite levels

A recent study conducted by the Mayo Clinic on fasting mice showed that when they reduced their food intake by 20 percent over 4 weeks there was actually a change at the cellular level in your stomach. The change in these cells in the stomach changed the capacity of the stomach to relax – leading the stomach to actually expand LESS – therefore not accommodating as much food, and allowing you to feel full sooner. The Mayo Clinic also performed studies on humans who lost at least 20 percent of their body weight and found similar results. You can read more about the study here. 

The researchers believe that short term fasting is very unlikely to produce the long term changes in the stomach. However, please be careful when reading this information to not take it to the extreme. For those suffering from anorexia, these people have a hard time both mentally and physically eating because they have created a situation in their stomach where it cannot relax to eat so they are unable to accommodate food. It is always important to talk to your doctor, nutritionist or a health care professional when you are looking to lose weight so you can do it in a safe manner.


  • all adults have approximately the same size stomach, regardless of weight
  • ghrelin and leptin play an important role and can be affected by the foods we eat
  • sugar, sleep deprivation and hormonal changes play a role in our food intake
  • long term changes in the amount of food intake can change our appetite levels

Had you always heard that your stomach shrinks when you don’t eat? Have you ever cut out sugar and noticed a difference in your appetite levels? Let me know in the comments if you’ve ever changed your eating habits and how they turned out! Don’t forget to check out my other posts – advice on how to start working toward better health, the dangers of not drinking enough water, and quick recipes that will help kick those sugar cravings!


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