Will Not Eating Make Constipation Worse?

November 3, 2025 •

4 min read

According to the Canadian Digestive Health Foundation, not eating enough—whether by skipping meals or restrictive dieting—is a major cause of constipation. A low caloric intake provides insufficient fuel for the digestive system, causing it to slow down significantly. This slowdown can lead to infrequent and difficult bowel movements, confirming that not eating can indeed make constipation worse.

Quick Summary

Undereating or skipping meals slows down the digestive system, leading to harder stools and worsening constipation. Insufficient caloric intake and reduced fiber and fluid consumption are key factors. Addressing dietary habits and reintroducing proper nutrition is crucial for improving digestive regularity and function.

Key Points

Slower Digestion: When you eat less, your body conserves energy by slowing down the digestive process, which can directly lead to constipation.
Lack of Fiber: Severely restricting food intake often means eliminating the high-fiber foods that are crucial for adding bulk and softness to stool.
Dehydration Risk: Undereating and skipping meals can lead to inadequate fluid intake, causing dry, hard stools that are difficult to pass.
Weakened Bowel Muscles: Chronic undereating, such as in eating disorders, can lead to the weakening or atrophy of intestinal muscles, further hindering motility.
Laxative Dependency: Misusing laxatives to counter constipation from undereating can worsen the problem over time by making the bowels reliant on them.
Restoration is Possible: Reintroducing regular, balanced meals with fiber and fluids helps normalize digestive function, even after prolonged restriction.

How Undereating Affects Your Digestive System

When you don't eat, your body's energy-conservation mechanisms kick in, and your digestive system's motility decreases. This means the muscles that move food and waste through your gut become less active. With less bulk from food and a slower transit time, your body absorbs more water from the stool, causing it to become hard, dry, and difficult to pass. This is the core reason why not eating can directly cause or worsen constipation.

The Lack of Bulk and Fiber

Dietary fiber, both soluble and insoluble, is essential for healthy bowel movements. Fiber adds bulk to the stool, helping it retain water and move smoothly through the intestines. When you restrict your food intake, you drastically reduce your fiber consumption, removing this vital component for regularity. The body simply has less material to convert into stools, and the small amount that is produced is more likely to be hard and compacted.

Inadequate Fluid Intake

Often, people who are not eating also fail to drink enough fluids, particularly water. Dehydration is one of the leading causes of constipation because it results in harder, drier stools. The colon's primary function is to absorb water, and if your body is already dehydrated, it will pull even more water from the stool, exacerbating the problem. Fluids are necessary to help fiber function properly and keep the digestive tract lubricated.

The Impact on Gut Motility

For those with severe undereating issues, such as anorexia nervosa, the effect on gut motility can be pronounced and persistent. The chronic lack of nutrition can lead to a condition called gastroparesis, or delayed gastric emptying, where the stomach takes an abnormally long time to empty its contents. This, combined with weakened intestinal muscles from underuse, can cause significant gastrointestinal distress, including severe constipation, bloating, and abdominal pain.

The Vicious Cycle of Laxative Abuse

Some individuals in a cycle of restrictive eating may turn to laxatives to deal with constipation, but this can actually make things worse. Chronic misuse of laxatives weakens the bowel muscles and nerves, creating a dependency for bowel movements. When laxative use is stopped, the underlying constipation can return with greater intensity, trapping individuals in a difficult cycle and potentially causing further digestive complications.

Comparison of Regular Eating vs. Undereating on Bowel Function


Feature	Regular, Balanced Eating	Undereating / Skipping Meals
Gut Motility	Consistent and regular stimulation.	Slows down significantly to conserve energy.
Stool Volume	Sufficient bulk from fiber and food content.	Low volume, leading to less frequent bowel movements.
Stool Consistency	Soft and easy to pass due to adequate hydration and fiber.	Hard and dry, as more water is absorbed by the colon.
Fiber Intake	High intake of fiber-rich foods (fruits, veggies, whole grains).	Low or nonexistent intake of dietary fiber.
Hydration Levels	Typically maintained with regular fluid consumption during meals.	Often compromised, leading to dehydration.
Bowel Muscle Tone	Healthy and functional due to regular use.	Weakens or atrophies due to underuse.

Natural Strategies for Digestive Regularity

To manage or prevent constipation related to under-eating, a multi-faceted approach is most effective:

Reintroduce food gradually: For those with restrictive eating, a slow and steady reintroduction of regular, balanced meals is essential. This allows the digestive system to re-adapt without overwhelming it.
Increase fiber intake: Focus on consuming plenty of fiber-rich foods, such as fruits, vegetables, whole grains, nuts, and legumes. Incorporate both soluble fiber (oats, apples) and insoluble fiber (whole wheat, carrots) for best results.
Prioritize hydration: Drink at least 8-10 glasses of water daily, especially when increasing fiber intake. Herbal teas and clear soups can also help add fluids.
Stay active: Regular physical activity, even a daily walk, can stimulate intestinal contractions and encourage regular bowel movements.
Establish a routine: Try to have meals and use the restroom at the same time each day to help regulate your body's internal clock for digestion.

Conclusion

Undeniably, not eating can and often does make constipation worse. The process is a direct result of the body's natural response to insufficient caloric intake: the digestive system slows down to conserve energy, and there is a lack of bulk, fiber, and fluids to form and pass stools effectively. Addressing this issue requires a return to regular, balanced eating habits that include adequate fiber and hydration. While the initial adjustment period might be uncomfortable for the digestive system, consistent nourishing will help restore proper function and alleviate constipation. If issues persist, it is always recommended to consult a healthcare professional. For more in-depth information on managing GI issues during recovery from eating disorders, the Centre for Clinical Interventions offers useful resources.

Frequently Asked Questions

Skipping a single meal is unlikely to cause severe constipation, but it can contribute to irregular bowel movements and a temporary slowdown of your digestive system, especially if it becomes a regular habit.

Eating too few calories provides less fuel and bulk for your digestive system. The body slows down its processes to conserve energy, resulting in less frequent and harder stools.

For some individuals, yes. Intermittent fasting can lead to constipation due to changes in eating patterns and potentially lower intake of fiber and fluids during the eating window.

The fastest relief involves rehydrating and consuming easy-to-digest, high-fiber foods like prunes, pears, or oatmeal. Taking a short walk can also help stimulate bowel activity.

Yes, you should definitely keep eating. Not eating will worsen the problem by further slowing down your digestive system. Focus on high-fiber foods and plenty of fluids.

Laxatives are not a good long-term solution and can create dependency and damage bowel function over time. It is best to address the root cause by reintroducing healthy eating habits.

It varies by person, but digestive function can improve within weeks of re-establishing a regular, balanced diet. For individuals with a history of severe restriction, it may take longer, and professional guidance is advised.