If you’ve noticed the numbers on the scale shifting unpredictably since being diagnosed with ulcerative colitis, you may wonder whether there’s a connection. While weight fluctuation can add to the confusion around this new diagnosis, losing or gaining weight with ulcerative colitis isn’t unheard of. Some people shed a few pounds when symptoms are active, while others gain as inflammation settles down or treatments take effect. Many experience both at different points in their lives.
These changes don’t mean that you’re mismanaging your condition. Instead, they simply reflect how your body is responding to inflammation, medications, and your evolving nutritional needs. Understanding what’s behind them can help you feel more informed and reassured as you navigate life with ulcerative colitis.
What is ulcerative colitis?
Ulcerative colitis is one type of inflammatory bowel disease (IBD), a group of conditions that involve ongoing inflammation in the digestive tract. In ulcerative colitis, this inflammation specifically affects the lining of the large intestine, also known as the colon. It often begins in the rectum and can gradually extend through part, or all, of the colon.
When the colon is inflamed, it can disrupt normal digestion and produce symptoms such as diarrhea, abdominal discomfort, fatigue, and changes in appetite or weight. Beyond digestive symptoms, both the inflammation itself and the treatments used to manage ulcerative colitis can influence how the body functions in broader ways, including body weight.
Can ulcerative colitis cause weight gain?
Yes, ulcerative colitis can lead to weight gain for some individuals, though experiences tend to vary widely. While IBD is typically linked to weight loss, weight gain is possible during periods of remission or after starting treatments that successfully reduce inflammation. Ulcerative colitis can also influence daily routines and eating habits, as people adjust their lifestyles to manage symptoms and maintain a state of remission.
What can contribute to weight gain with ulcerative colitis?
Gaining weight with ulcerative colitis often results from several overlapping factors rather than just one cause. Some of these factors include:
Improved nutrient absorption during recovery
As symptoms ease and the gut begins to heal, appetite improves, and the body is then able to absorb and use nutrients more effectively. For some people, this phase of recovery can come with gradual weight gain, especially when a higher-calorie diet is introduced.
Medication side effects
Certain medications used to manage ulcerative colitis can also influence weight. Corticosteroids, in particular, are known to increase appetite, cause the body to retain fluid, and alter how fat is stored and distributed when used for longer periods.
Reduced physical activity
Fatigue is another usual symptom among people with IBD, including ulcerative colitis. Chronic inflammation, combined with nutritional deficiencies (particularly in iron, which may give rise to anemia) and emotional stress, all contribute to persistent tiredness, making physical activity rather challenging. When movement decreases, body weight may slowly increase, even without changes in diet.
Fluid retention and bloating
Not all apparent weight gain in ulcerative colitis represents lasting changes in body fat. Inflammation, gas, or side effects from certain medications may result in fluid retention, making the abdomen feel swollen. This bloating tends to give the impression of increased body mass, temporarily raising the number on the scale or making clothes feel tighter. Still, weight can be expected to normalize once bloating subsides.
Higher food intake
People tend to consume significantly more food once symptoms ease to make up for previously lost weight. Emotional factors like stress and anxiety around symptom management have also been known to play a role in this increase.
Does ulcerative colitis cause weight loss?
Yes, weight loss is a widely recognized part of uncontrolled ulcerative colitis, particularly during symptom flares. When inflammation is active, or flares are prolonged, it may be difficult to meet your body’s needs, leading to a drop in weight.
What can lead to weight loss with ulcerative colitis?
Similar to weight gain in ulcerative colitis, various elements may induce a drop in body weight:
Metabolic changes from chronic inflammation
When inflammation is active, the body enters a “catabolic state,” where the body is burning more energy than it is taking in. Inflammatory chemicals, called cytokines, are then released and tend to suppress appetite and alter how the body processes nutrients.
Diarrhea
Frequent, loose bowel movements are a hallmark symptom of active ulcerative colitis and a huge contributor to weight loss. When food moves too quickly through the digestive tract, the body also has less time to absorb nutrients and calories, creating a disconnect between what the body consumes and what it actually retains and uses.
Reduced food intake due to symptoms
Abdominal pain, cramping, bloating, nausea, fatigue, and feelings of urgency can make eating physically and emotionally challenging. Some people eat less because they feel unwell, while others avoid meals out of concern that food will trigger or worsen symptoms. Over time, consistently eating smaller portions, skipping meals, or cutting out entire food groups can cause a calorie deficit and unintentional weight loss.
Poor absorption of nutrients
Active inflammation in the colon can compromise the body’s ability to absorb nutrients, fluids, and electrolytes efficiently. Even when you’re eating enough, your body may not fully utilize these nutrients. Repeated flares or prolonged disease activity can increase the risk of deficiencies in iron, vitamin D, B vitamins, and other essential nutrients.
Muscle loss from undernutrition
Weight loss in ulcerative colitis doesn’t always mean losing body fat alone. In some cases, the body may also lose lean muscle mass. When the aforementioned factors stack up, they can translate to undernutrition, which simply means the body isn’t getting or properly using the nutrients it needs. Eventually, this can prompt the body to break down muscle for energy. Muscle loss may affect physical strength, energy levels, immune function, and recovery in general.
That said, muscle loss doesn’t happen to everyone with ulcerative colitis. The risk often varies depending on how severe the disease is, how well treatments are controlling inflammation, and whether nutritional needs are being met.
When weight gain or weight loss may warrant medical attention
Changes in body weight are often an expected part of living with ulcerative colitis. As symptoms shift between flares and periods of remission, it’s normal for your body to respond accordingly. However, there may be instances that require a closer look — not as a cause for alarm, but as a way to make sure you’re getting the support your body needs.
It may be helpful to consult a medical professional if:
- Weight gain or weight loss happens rapidly or continues over time without a clear reason
- Weight changes occur alongside worsening symptoms, such as persistent diarrhea, blood in the stool, or a significant drop in appetite
- Weight loss begins to impact daily life, making it difficult to maintain strength, focus, or enough energy for everyday activities
Your gastroenterologist or dietitian can help determine what may be contributing to these physical changes, whether it’s inflammation, side effects from medications, shifts in nutrient absorption, or something else entirely. Addressing weight changes early with the right support can help you stay ahead of potential complications, protect your overall health, and feel more confident managing ulcerative colitis.
Find nutrition support tailored to your needs at Health Loft
How your body responds to ulcerative colitis is never an indication of personal failure. Changes in weight, as well as in appetite and energy levels, are often influenced by various factors that are outside of your control. Because these needs can change over time, individualized care should be a priority.
At Health Loft, our registered dietitians who specialize in ulcerative colitis understand that support should evolve with you. Whether your symptoms are active or well-managed, guidance is tailored to your current nutritional status, lifestyle, and recovery goals.
We work with you alongside your healthcare team to ensure that you’re staying nourished and informed as you navigate potential weight loss or weight gain caused by ulcerative colitis. Rather than unnecessarily restricting your food choices and eating habits, we focus on practical, flexible strategies that adapt to how you’re actually feeling, helping you meet your dietary needs while minimizing feelings of fear or confusion.
Connect with a Health Loft dietitian and discover realistic, compassionate, and sustainable ways to approach nutrition and support your body.
This article was reviewed by Haleigh Mann, MS, RDN, LDN. It is intended for informational purposes only and does not replace personalized nutritional advice.
