It’s proven that women who are undergoing chemotherapy for breast cancer decrease their activity, which leads them to gain weight.

In addition, women sometimes eat more frequently. One reason may be they’re trying to settle their stomach in order to tolerate the chemo. Another reason is that chemotherapy puts women aged 50 to 55 years into a deeper menopause, which slows the metabolism. Steroids are needed to help prevent allergic reactions to the chemo and to decrease nausea and vomiting, and steroids drive people to eat more.

The biggest issue for breast cancer patients is having no estrogen. As women’s estrogen levels fall off, they gain weight. You have to be very controlled in your diet to avoid gaining weight once post-menopausal, which is quite difficult to do. That’s a huge issue for my patients.

Once women go into menopause, their metabolism completely changes. As a result, whatever body type they were before onset of menopause — overweight, thin or somewhere in between — is irrelevant. Menopausal women uniformly develop truncal obesity; they gain weight in their abdomen.

We know that weight gain is more common in association with breast cancer treatments than weight loss. In addition, we know that patients who gain a significant amount of weight during their breast cancer treatment — that is, 10 percent or greater than their baseline weight — are at an increased risk of breast cancer recurrence.

It’s clear to me that if you look at the evolution of cancer, exposure to lifestyle behaviors including diet and exercise can either slow down the process — or the lack of engagement in those behaviors can accelerate that process. It’s becoming clearer and clearer what the specific mechanisms are. Further reading.

This is a very exciting time in the field of nutritional and exercise oncology. We’re finding that it’s quite possible that what we eat and how we move or don’t move while undergoing cancer treatment could actually impact whether we can withstand and complete the treatment. And that, in turn, could impact long-term survival.

People are becoming more cognizant of the contribution of their lifestyle, including diet and activity levels, to the tolerability of their cancer treatment and to prevention of recurrence.

What we need is a systematized data collection for the current state of patients’ diet and physical activity. What are people doing on average, in terms of their diet and exercise, after a cancer diagnosis? How is that contributing to the tolerability of their treatment and to their cancer outcomes? We’re doing that in my clinic right now: When I see a new patient, we automatically email them a link to the National Cancer Institute’s dietary health questionnaire.

Weight gain during cancer therapy has been associated with less efficacy. Fifteen years ago, you probably wouldn’t even talk about exercise and obesity with an oncology patient.

The observational studies are really compelling and very consistent: Individuals who eat a healthy diet — as defined by a Mediterranean diet or what you would see on the USDA website — maintain a healthy weight and are physically active on a regular basis are less likely to have a diagnosis of cancer than those who are overweight, eat a poor diet and are sedentary.

There’s an aching need for us to get very specific in our recommendations. For instance, where are you in your treatment trajectory, from just having a cancer diagnosis all the way to the end of life? What we recommend for somebody going through radiation and chemotherapy will be different than what we recommend for somebody who’s a long-term survivor and very healthy.

I’ve been aware of this issue since I began my career in the early 1990s. Later, I got involved in the Women’s Health Initiative Dietary Modification Trial, a $320 million study with 48,835 women. We’ve seen that women who have three or four metabolic syndrome components have about a three-fold increased risk of dying of breast cancer — but we could reduce that risk by 69 percent through dietary intervention.

Everything is a very delicate balance. If something is wrong in one organ, it can impact the health of other organs as well. During obesity, the adipose tissue becomes dysfunctional. The immune system senses that something is wrong, and uses the circulatory system as a telephone network to call back up from immune cells located throughout the host.

The results [of the Physical Activity and Lymphedema (PAL) Trial] showed that twice-weekly, progressive strength training was not only safe for women with and at risk for lymphedema, but in fact prevented lymphedema in those who were at risk and reduced the likelihood of the need for treatment for lymphedema by 50 percent in those who already had lymphedema.

I think the psychologically depressing aspect of having breast cancer also makes women gain weight. Following a diagnosis of breast cancer, women tend to broaden their eating. Alcohol plays a role, too. As women get older, many drink more alcohol, which has more empty calories in it.

The mental health of a person going through a cancer diagnosis is certainly contributory to their general health, including their metabolic health (certain anti-depressants contribute to weight gain — tricyclic, monoamine oxidase inhibitors, and long-term use of SSRIs). And so, we screen everyone for depression, anxiety or even subclinical depression. As the person’s oncologist, I always try to get a sense of how they’re doing mentally.

I think it’s about having appropriate guidance. We have a specialty in our midst — oncology nutritionists — who are registered dieticians and know how to work with oncology patients. They’re not that expensive, and I think people would do so much better if they had high-quality recommendations during and after their cancer treatment.

So I think it’s a matter of getting people connected to the right kind of expertise. I don’t think obese people are less likely to want to eat healthy. I think they just may not know what they’re supposed to be eating.

I caution patients during treatment that their weight needs to remain under control in order to consolidate the cure and not increase the risk of recurrence. As most people know, steroids can certainly induce metabolic dysfunction, like hyperglycemia or prediabetes. Further reading.