Could weight management be an overlooked element in survivors’ arsenal following breast cancer? Although large losses of body fat and muscle remain a critical problem typical of some cancers, many cancer survivors today are overweight at the time of diagnosis, and remain so following treatment. Mounting evidence links pre-diagnosis obesity and undesired post-diagnosis weight gain with worse outcomes among cancer survivors.
Here, in the first section of a video interview with Maura Harrigan, MS, RD, CSO, you’ll get the glass half-full view: steps to reach and maintain a weight that is healthful for each individual cancer survivor may promote recovery and long-term health, and provide a positive way that cancer survivors can do something good for themselves.
Maura Harrigan is a registered dietitian who is a board-certified Specialist in Oncology Nutrition. Ms. Harrigan is a research associate at the Yale School of Public Health, and Nutrition Director of the Cancer Survivorship Clinic at Yale Cancer Center. She is involved in a key research study there known as the Lifestyle, Exercise and Nutrition (LEAN) Study, which may have major implications for optimizing care of breast cancer survivors.
Following the video, read on for my take on how to put this message in context for eating and lifestyle choices that promote cancer survivors’ health.
(Email subscribers, you’ll need to go to my Smart Bytes® blog to view the video.)
If you associate cancer with huge weight loss, it’s hard to grasp, but excess weight and weight gain have now become a more common problem than underweight among breast cancer survivors. Some cancers, such as mouth, throat and lung cancers, are still often linked with large weight loss, but that’s far from true for survivors of many other cancers.
In our interview, you probably noticed that although studies in research populations report weight gains among breast cancer survivors as quite common but somewhat smaller than in years past, Maura Harrigan says that in her clinical practice, gains of 20 pounds or more remain typical.
About one in three breast cancer survivors had more than a five percent weight gain from pre-diagnosis to about two years post-diagnosis in one analysis combining several studies. But research indicates that breast cancer survivors often continue to gain weight after the two-year mark, including those whose weight was stable during treatment.
Why is weight gain so common?
Weight gain has become more common in part because of improvements in cancer treatment and ability to avoid or control chemotherapy-related nausea that used to make eating a bigger and more widespread challenge than today. In the case of breast cancer, when chemotherapy induces menopause suddenly, the effects on weight and muscle loss tend to be more drastic than in normal aging, and other hormone-impacting medications may have similar effects. Cancer-related fatigue that is widespread among cancer survivors, and joint pain that is a common side effect of aromatase inhibitors and other endocrine therapies, can lead to decreased physical activity that promotes weight gain among cancer survivors.
Some may unintentionally increase calorie consumption as they use food to try to cope with fatigue, insomnia or depression. Others may intentionally increase calories due to misinformation among cancer survivors and their families. People often so strongly connect cancer with “wasting away”, that they boost calorie intake or ply their loved ones who have cancer with high-calorie foods, not realizing that this may not be necessary, and may even be counter-productive.
Why bother about weight or weight gain in cancer survivors?
Among cancer survivors, those who are obese at the time of cancer diagnosis face increased risk of recurrence and mortality. This link is most strongly documented for breast cancer, with combined studies linking obesity to increased cancer recurrence and poorer survival (from breast cancer and other causes of death). Although obesity only increases risk of postmenopausal breast cancer, it is linked with reduced survival in both premenopausal and postmenopausal women, especially with estrogen receptor-positive cancer.
Even people at a healthy weight when diagnosed with cancer may gain weight during cancer treatment and in the years that follow. One study found that during the period from one or two years post-diagnosis to about seven or eight years post-diagnosis, each additional 11-pound gain among breast cancer survivors was associated with a further increase in risk of death due to breast cancer and due to heart disease.
Some evidence shows women of normal weight most likely to gain significant weight, and most likely to show poor outcome related to gain. While studies continue, many researchers concur with the recommendation you heard from Maura Harrigan in our interview, that it’s best if breast cancer survivors take steps to avoid undesirable weight gain during and after treatment.
The link between overweight, obesity and weight gain to worse outcomes among cancer survivors is not about “weight” per se, but high body fat. Excess body fat tends to promote chronic low-grade inflammation. It can also lead to elevated levels of insulin and related growth factors (such as IGF-1), which promote cell growth and are linked to greater recurrence and mortality in breast cancer survivors. Excess body fat also increases postmenopausal women’s levels of estrogen, which promotes growth of estrogen-sensitive cancers. Increased overall mortality among survivors of breast and other cancers also reflects impact on heart disease, which is actually the primary cause of death among many cancer survivors.
Will losing weight help?
The question that research has not yet clearly answered is what benefits cancer survivors who are already overweight or obese can expect from weight loss, and how much loss and what methods provide greatest protection.
Studies among cancer survivors (and people without cancer) show that weight loss by people who are overweight can produce changes in estrogen, inflammation and insulin resistance that seem involved in the link between excess body fat and worse cancer outcomes. For example, in one intervention trial, breast cancer survivors who lost 5% or more of their starting weight had greater drops in insulin and bioavailable estrogen (in post-menopausal women) than women who did not achieve the 5% weight loss goal. For now, intervention trials addressing this issue are sparse, but more are underway.
Despite these many reasons to expect weight loss to improve outcomes among cancer survivors who are overweight or obese, it’s not so simple. One analysis pooling four observational studies of breast cancer survivors shows lowest mortality rates in those who maintained a steady weight in the first few years following cancer diagnosis. Although weight gain was linked to worse prognosis, weight loss of ten percent or more was also associated with increased mortality from non-breast cancer causes.
Data like this are challenging to interpret. Authors of the pooled analysis of breast cancer survivors suggest that the increased mortality with largest weight losses may reflect an unhealthy loss of lean body tissue (which can occur even if obese). The same total weight loss may differ in its effects depending on individual circumstances.
- Fat vs. lean loss: Loss of lean body mass (muscle and other body tissues) is associated with poor outcomes in both cancer and heart disease. Observational studies can’t distinguish between intentional weight loss from healthful changes in eating and physical activity versus unintentional weight loss that may signal deteriorating health or malnutrition, and often involves greater loss of lean muscle.
- Type of cancer: Among breast cancer survivors, several studies link obesity to poor outcomes only in women with estrogen receptor-positive cancer, so the importance of weight loss may vary with cancer type.
- Medical specifics: Age, current state of lean muscle and additional medical conditions may also influence effects of weight loss.
For survivors of other cancers
Obesity does not seem to increase risk of prostate cancer, but obesity and adult weight gain increase the risk of more aggressive forms of prostate cancer, and of death due to prostate cancer itself and due to heart disease. Among colorectal cancer survivors, it’s not clear whether modest overweight poses additional risk, but more severe obesity is linked to increased recurrence. Risk of several other cancers clearly increases with excess body fat, but we don’t have enough research yet to know whether weight loss by survivors of colorectal or other obesity-linked cancers makes a difference in survival. For now, recommendations about avoiding undesirable weight gain and seeking healthful, modest weight loss as medically appropriate seem to apply.
What’s the take-home? Chronic low-grade inflammation and elevated insulin and related growth factors are tied to risk of cancer, type 2 diabetes and heart disease. So the best research-based strategy for cancer survivors who are normal weight with healthy body composition is to avoid weight gain. For those who are already overweight or obese, rather than reaching for a statistical “ideal” weight, modest weight loss is recommended by the American Institute for Cancer Research and the American Cancer Society (unless unadvisable for individual medical reasons), which may mean a 5 to 10% loss — or even less. With a focus on fat and lean weight, rather than just “weight”, healthy weight loss is achieved through eating and physical activity choices that minimize loss of lean muscle and bring modest loss of excess body fat.
Where does physical activity fit into all this? And what strategies does Maura Harrigan, MS, RD, CSO find most helpful for the cancer survivors with whom she works? Come back for more from our interview in future Smart Bytes® posts! Meanwhile, please feel free to share this post with others!
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