Why do I get constipated when I go on a diet?

“I can’t poop. Why am I constipated?”

I get this question all the time from people who are completely baffled.

“How can it be that I’m eating all of these fruits and vegetables and I haven’t pooped for days? I can’t believe I’m constipated. Shouldn’t I have the opposite problem?”


Fruit and vegetables are associated with loose stools, and even a recommended solution to get things moving, but many a dieter, especially those who are just getting started with weight loss suffer from constipation.


Constipation is hard, dry stools that are difficult to pass. The National Institute of Diabetes and Digestive and Kidney Diseases defines constipation as fewer than three bowel movements a week. Although there is no passing of the bowel movement, the urge doesn’t stop, making the condition both frustrating and painful.  Sometimes home remedies and over-the-counter medicines don’t help at all. They just seem to make it worse.


Why would dieting, especially eating mostly plants, cause constipation? The reason may be any of the following. If you have a sensitive stomach or irritable bowel syndrome, it’s even more likely that you’ll have poop problems.

  1. Making a big change in food choices
  2. Big change to eating habits
  3. Cutting calories by skipping meals/ erratic eating schedule
  4. Drinking too little water
  5. Increasing fiber intake too drastically (fruit, vegetables and especially legumes which are the foundation of many weight loss plans are high in fiber)

When vast changes are made to both what and how we eat, it can cause constipation. Once your body gets used to the new way you’re eating, you should get relief from constipation. It must also be noted that your constipation seems to be caused by your diet, but it’s merely a coincidence. It may actually not be related at all.

Other conditions that may be the culprit include hypothyroidism (which may also explain your weight issues), painkillers, vitamins (many weight loss plans suggest a daily multi vitamin), antidepressants, antacids, and blood pressure medications.

When to see the doctor

While occasional constipation doesn’t warrant a call to the doctor, if your constipation has been going on for a week or more, and your home remedies haven’t corrected the problem, it’s time to call the doctor.

If you experience any combination of any of these four symptoms—abdominal pain, an inability to pass gas, vomiting, and stomach bloating—you might actually have a bowel obstruction. In that case, skip the call and get to the emergency room.

Assuming that your problem is completely related to going on a diet try these strategies to avoid constipation.

Strategies to avoid constipation

  • Eat Slower. Eating slower is more than just a way to recognize satiety before you’ve eaten more than enough to be “full.” Slowing down your eating might also reduce problems with gas. People who eat fast often swallow extra air which leads to more gas.
  • Scheduled Eating. Erratic eating patterns are a cause of gas and constipation. Skipping meals as a weight loss strategy is not a good idea. Try to eat at about the same time each day to help alleviate both gas and constipation
  • Eat the Right Diet. Your weight loss diet may not be balanced. It should consist of adequate fiber and healthy foods that provide needed vitamins and minerals.
  • Adequate Water. Water is an important element to keep the bowels functioning properly. Drinking fluids with your meals also increases the production of gas for many people.
  • Move to Keep Things Moving! Exercise helps constipation by decreasing the time it takes food to move through the large intestine. That will limit the amount of water absorbed from the stool into the body.  Aerobic exercise accelerates breathing and heart rate. This helps to stimulate the natural contraction of intestinal muscles. Intestinal muscles that contract efficiently help move stools out quickly.




Jackie Conn

About Jackie Conn

Jackie Conn is married and has four grown daughters and four grandchildren. She is a Weight Watchers success story. She's a weight loss expert with 25 years of experience guiding women and men to their weight-related goals. Her articles on weight management have been published in health, family and women's magazines. She has been a regular guest on Channel 5 WABI news, FOX network morning program Good Day Maine and 207 on WCSH.