Cancer Benefits and Risks From Ozempic, Wegovy, and Other Weight Loss Drugs

Neil Iyengar, MD, is seen talking with a patient.

Neil Iyengar, MD, is a breast cancer oncologist and an expert on the relationship of cancer with diet, excess body weight, and obesity. Many of his patients ask him about the new weight loss drugs including Ozempic and Wegovy.

Ozempic, Wegovy, and related weight loss drugs have become some of the world’s most talked about medications in a remarkably short amount of time.

Much of the conversation centers around celebrities who credit the drugs with helping them shed weight and look trimmer, sometimes very quickly.

But doctors and researchers are largely focused on whether the medications may be an important new tool for treating the epidemic of obesity and related conditions that can cause serious health problems — including a greater risk of cancer.

“There are at least 13 types of cancer, including breast, prostate, endometrial, and others that we know are linked to obesity,” says Neil Iyengar, MD, a breast cancer oncologist at Memorial Sloan Kettering Cancer Center (MSK) and a nationally recognized expert on the relationship of obesity, metabolic health, and cancer.

“Separate from obesity,” Dr. Iyengar adds, “having higher levels of body fat is associated with an increased risk of several forms of cancer.”

He continues: “I foresee that this class of drugs will revolutionize obesity and the cancer burden that comes with it, if people can get access. This really is an exciting development.”

Dr. Iyengar cautions that these are early days for these medications with much research yet to do. However, “Many patients ask me about these medications,” he says. Here, he provides answers to the questions his patients ask most often.

What are these new weight loss drugs?

The best known right now are:

These are known as GLP-1 agonists. They activate the GLP-1 receptor that stimulates the production of insulin, which regulates blood sugar, as well as delivering several other effects.

Because they affect insulin, these medications were originally developed to treat diabetes. Ultimately, their weight loss effect was recognized.

It’s important to know that the current Food and Drug Administration (FDA) indication (or guidance) for being treated with one of these drugs is obesity plus a metabolic disorder related to obesity, like diabetes. A cancer diagnosis currently does not qualify as a reason for treatment with these drugs. MSK is conducting research to determine if cancer should be added as a reason for treatment with these medications.

Do they really help people lose weight?

They do, and the weight loss is even better when combined with healthy lifestyle choices.

There have been weight loss drugs for a long time, but they provided only moderate weight loss and had a lot of side effects. This new class of drugs are much more successful in treating obesity and inducing weight loss, and have manageable side effects.

How do Ozempic, Wegovy and similar weight loss drugs work?

Think of it as constantly putting you in a post-meal state, where you feel full and aren’t hungry, so you don’t feel the urge to eat. This happens through several different mechanisms, some of which are not fully understood. These include the following hormones:

  • Ghrelin: The drugs regulate the hormone ghrelin, which is produced in the stomach and is basically the hunger hormone that signals to your brain that you need food.
  • Leptin: This hormone is the opposite of ghrelin. It is produced in your fat cells and tells your brain that you’re full and don’t need any food.
  • Insulin: A person’s insulin level is also regulated by the medication and slows down the working of your stomach, called gut motility, so you feel full longer.

All these factors work together, and there is direct stimulation of the brain telling you that you don’t have cravings and feel full — just like after a big meal.

How does weight loss affect cancer risk?

We know obesity — and even high body fat — puts people at greater risk for multiple forms of cancer. It can be a challenge to get a healthier body composition for many people, and these medications can help jump-start the effort.

By reducing food cravings, these drugs can lower the consumption of highly processed food, which is particularly bad for overall health, including cancer risk. There is also evidence to suggest cravings for alcohol are lowered.

Lifestyle modifications are crucial — a medication alone is not a long-term fix. For people with cancer, I especially recommend a high-fiber, plant-forward diet and consistent exercise. For people with breast cancer, the MSK Healthy Living Program helps to implement these lifestyle recommendations. Getting started with those kinds of lifestyle changes may now be easier for some people thanks to an appropriate use of the new weight loss medications.

Can Ozempic, Wegovy, and similar weight loss drugs help people diagnosed with cancer?

We simply don’t have the data for somebody who has just been diagnosed with cancer. I also worry about anything that could disrupt urgent treatments like chemotherapy or radiation therapy or immunotherapy at the beginning of cancer therapy. For instance, there can be gastrointestinal side effects with these weight loss drugs, and that could interfere with some cancer treatments.

On the other hand, if someone has been on cancer treatment for a couple months and is tolerating it well, it may be fine to use these weight loss medicines. For people on long-term hormonal therapy, we’ve anecdotally seen that use of concurrent weight loss medications appears to be feasible. In fact, some patients quit taking their hormone therapy because it can be associated with weight gain, and the new weight loss medications might be a solution. Of course, anyone on cancer therapy and interested in starting a weight loss medication should first check with their oncologist.

We definitely need clinical trials to determine the safest and most effective approach to medical weight loss in the setting of cancer treatment.

In the cancer setting, who could these medicines help best?

  • People who want to prevent cancer in the first place, if they are obese or significantly overweight.
  • People who have been on cancer treatment for quite a while or are looking to reduce the chance of recurrence after finishing treatment by reducing their body weight.

Of course, people would need to discuss the best option with their care team.

What are the side effects of these drugs?

There can certainly be gastrointestinal side effects, including nausea and vomiting for some people, which are usually manageable.

Some research has also raised the risk of more serious side effects, including:

  • Suicidal thoughts: Research in Europe suggested these drugs could lead to suicidal thoughts. Remember, these medications affect the brain pathways responsible for hunger signaling, and while there can be positive aspects to medications that involve the brain, we need to be aware of any negative repercussions.

This side effect was quite rare. In fact, the FDA concluded that there were no concerns about suicidal ideation caused by these drugs. However, if a person taking these drugs notes a depressed mood or change in anxiety level, they should discuss it immediately with their provider.

If you or someone you know may be experiencing a mental health crisis or contemplating suicide, call or text 988. In emergencies, call 911, or seek care from a local hospital or mental health provider.

  • Thyroid cancer: A very low risk of thyroid cancer, specifically medullary thyroid cancer, has been associated with use of these drugs, and this is of particular concern to people already diagnosed with cancer. Thankfully, this is quite rare. Overall, the people who are good candidates for this medication often have health risks that are greater than the low risk of thyroid cancer. Nonetheless, this is an important risk/benefit discussion that should factor in health risks and patient priorities.

It’s worth noting that some research suggests the medications may actually protect against some forms of cancer, including colorectal cancer, for reasons that go beyond reducing obesity. However, much more research is needed — at this point, this is just an interesting hypothesis.

Overall, I’m very excited about the development of this class of drugs as a new and effective tool, in addition to lifestyle optimization, for reducing the health risks associated with obesity and metabolic disorders.

VIDEO | 01:21

Lowering Cancer Risk With GLP1 Agonist Weight Loss Drugs & A Healthy Lifestyle

Neil Iyengar, MD, talks about the new class of weight loss drugs and how they might be a part of an effective risk reduction strategy for developing cancer or cancer reoccurrence.
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