‘I'm an Oncologist-This Is the First Body Change I'd Never Ignore'
Cancer is a sneaky disease, and symptoms of it often show up slowly, making it hard to know what you're dealing with. While some forms of cancer cause no outward symptoms, others may be noticeable but easy to dismiss as something else.
"Cancer generally hijacks your body's native pathways rather than introducing foreign processes, so it is much harder for the body to even recognize that something is wrong," Dr. Ketan Thanki, MD, colorectal surgeon with the MemorialCare Todd Cancer Institute at Long Beach Medical Center in Long Beach, CA, tells Parade. As a result, symptoms may be mild, nearly unnoticeable or could be brushed off as being caused by something much less severe before you realize what's really behind the change in your health.
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There are a lot of forms of cancer, and each has its own unique characteristics. With that, it's hard to say for sure that any one symptom is definitely a sign of cancer.
But Thanki says there's one symptom in particular that you should get checked out. You may not notice it at first, but once you do, it's time to get evaluated. While it's not a slam-dunk symptom of cancer-few things are-it's typically a warning sign that something is off with your body. Here's why.
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The Body Change You Should Never Ignore, According to an Oncologist
It's unexplained weight loss. Meaning, weight loss that doesn't happen as a result of a change in your diet or exercise routine.
Again, there are a lot of health conditions that can have this as a symptom, but Dr. Thanki says that most are severe enough that you should have them investigated.
"The conditions that cause unexplained weight loss include malignancy, uncontrolled diabetes, hyperthyroidism, HIV, tuberculosis, heart failure, COPD, inflammatory bowel disease, and severe depression or anxiety," he explains. "None of these should go unaddressed."
Unexplained weight loss can come on slowly at first, making it more difficult to detect. "Immune and inflammatory responses are generic," Dr. Thanki tells Parade. "When the body recognizes that something is wrong, the pathways that are set in motion are the same regardless of trigger: Malaise, fevers, weight loss and appetite loss."
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Whether you have a tumor that causes an intestinal blockage or interferes with how your body burns energy, the weight loss may be subtle at first, Dr. Thanki says. This is because tumors typically grow slowly, he says. But as the tumor is growing, you're slowly losing weight.
"Weight loss in cancer reflects cachexia, a metabolic syndrome driven by tumor-secreted cytokines that actively break down muscle and fat even when caloric intake is adequate," Dr. Thanki says. "It's not simply ‘the tumor consuming calories.'"
It's also possible to feel off when you have cancer without realizing what's driving this, Dr. Thanki says. That can make you feel less hungry than usual, which can lead to unexplained weight loss, he adds.
Other Sneaky Signs of Cancer To Be Aware Of
There are a few other potential symptoms of cancer that should encourage you to be seen by a doctor. Dr. Thanki recommends keeping these on your radar:
- Fevers or night sweats
- Fatigue
- New, persistent headaches
- Neurological changes
- Personality changes
- Voice changes like hoarseness
- Bone, back, joint or muscular pain
- Changes in your bowel or bladder habits
- New constipation
- Blood anywhere that it shouldn't be
- New lumps or sores
- Changing moles
Of course, if you're dealing with unexplained symptoms that aren't on this list, it's still a good idea to get them checked out by a healthcare professional. They can do a thorough evaluation to help you get answers.
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Source:
- Ketan Thanki, MD, colorectal surgeon with the MemorialCare Todd Cancer Institute at Long Beach Medical Center in Long Beach, CA
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This story was originally published June 9, 2026 at 7:50 AM.