Weight Loss, Cancer and the Role of Metabolism

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In this episode, Diane Reidy-Lagunes speaks with Neil Iyengar, a breast medical oncologist and MSK’s leading researcher on diet, metabolism, and cancer. Together, they debunk myths surrounding diet trends, exercise, and the relationship between fat tissue and cancer.

Cancer Straight Talk from MSK is a podcast that brings together patients and experts, to have straightforward evidence-based conversations. Memorial Sloan Kettering’s Dr. Diane Reidy-Lagunes hosts, with a mission to educate and empower patients and their family members.

If you have questions, feedback, or topic ideas for upcoming episodes, please e-mail us at: [email protected]

Show transcript

Dr. Diane Reidy-Lagunes (00:02):

How often do you think about your weight? Be honest. It turns out the vast majority of Americans report being overweight or obese, but studies show that not one popular diet actually works. And to top that, 13 different types of cancers are linked to poor metabolic health. But the good news is that there's growing body of research suggesting that nutrition can play a significant role in preventing cancer. And studies are now testing if certain diets can improve outcomes in patients with cancer. Okay listeners, get ready for some easy-to-digest science about your metabolic health. Hello, I'm Dr. Diane Reidy-Lagunes from Memorial Sloan Kettering Cancer Center, and welcome to Cancer Straight Talk. We're bringing together national experts and patients fighting these diseases to have straightforward evidence-based conversations. Our mission is to educate and empower you and your family members to make the right decisions and live happier and healthier lives. For more information on the topics discussed here, or to send your questions, please visit us at mskcc.org/podcast. Today, I am honored to have my esteemed colleague and friend Dr. Neil Iyengar, a breast medical oncologist and leading researcher on the relationship between diet, metabolism and cancer. Neil, welcome to the show.

Dr. Neil Iyengar (01:33):

Thanks so much, Diane. It's such a great pleasure to join you.

Dr. Diane Reidy-Lagunes (01:36):

It's an honor to have you here with us. So Neil, the weight loss and diet market is valued at $192.2 billion. How does such a huge industry with a 95% failure rate survive and what are we doing wrong?

Dr. Neil Iyengar (01:54):

I love that question because that is really what has prompted myself and a lot of us to take a deep dive into this field. I think the numbers that you just outlined really underscore how weight, metabolic health, our nutrition, our physical activity, how we are surrounded by this every single day. Once we start to think about the physiological or bodily processes that go along with weight loss and that go along with metabolic health, we really need to keep in mind that a scientific approach to understanding the biology and how what we do in our daily lives impacts that biology, might improve that success or failure rate, as you mentioned.

Dr. Diane Reidy-Lagunes (02:37):

And so tell us, what exactly is metabolic health when you're describing that?

Dr. Neil Iyengar (02:42):

Yeah, great question. And this is really how multiple components of our body's processes and physiology or biology impact our hormonal balances, our energy balance—which is how we balance our calories in and energy out—as well as our body fat levels, inflammation – all of this is incorporated into metabolic health. And I think the bottom line here is our metabolic health is how our metabolism interacts with the various processes going on in our body.

Dr. Diane Reidy-Lagunes (03:15):

So let's talk about this link to cancer. So people say that fat is potentially a carcinogen. Carcinogen like smoking a cigarette. Can you explain a little bit about how that could possibly even work?

Dr. Neil Iyengar (03:29):

So I think we need to differentiate between the fat that we take in as part of our diets, as well as the fat tissue that we have in our body. We do know that the fat tissue that we have in our body is not a static or stand-still organ or inactive tissue as it was once thought to be. Our fat tissue is very dynamic. There are many things going on in our fat tissue. And the health of our fat tissue is critical not only to our metabolic health but, as we're learning, our risk of cancer and our response to cancer therapy. If our fat tissue is not healthy and not doing the processes that it's meant to do, then we may be exposing ourselves to a chronic carcinogen. And this is why I view something like obesity, especially unhealthy obesity, as a chronic carcinogen.

Dr. Diane Reidy-Lagunes (04:19):

And how do we know what it is supposed to do, or if it's misbehaving?

Dr. Neil Iyengar (04:24):

This is what we're spending a lot of time researching. We know that the basic function of fat tissue is to take in energy or calories and store it in a healthy way. Oftentimes when we are in a constant state of energy excess, or excess calories, the fat tissue becomes overwhelmed and it's not able to store energy appropriately. Some of that energy spillover can then lead to fat tissue dysfunction – things like inflammation, overgrowth of the fat tissue, fat tissue that our bodies simply cannot support – and that leads to a number of disrupted and potentially harmful processes.

Dr. Diane Reidy-Lagunes (04:59):

And how would I know my body mass percentage? Like, does that matter and is that something that I should be calculating?

Dr. Neil Iyengar (05:05):

I would say yes. The body mass index is one of our oldest tools for categorizing our metabolic health, if you will. And the body mass index is our weight in kilograms divided by our height in meters squared. It is a good start to help us understand what category we may fall into, but there are other tests – like understanding our body composition – that can better personalize our body's metabolic health.

Dr. Diane Reidy-Lagunes (05:33):

Got it. And that composition and those tests, can kind of patient do that themselves? Or is that something that their doctor does?

Dr. Neil Iyengar (05:39):

Yeah, absolutely. So one of the gold standard ways of measuring body composition is through a scan called a DEXA scan – it's basically an x-ray. And most doctors will order this to assess whether a person has osteoporosis, a condition of the bones. Well it turns out we can use the same test to measure body composition, and it's really quite accurate. Now it's not often covered by insurance, unfortunately, because we're still trying to get to the place where these types of tests are done routinely, but it can be done by a primary care doctor as part of preventative healthcare. Also, if this is not accessible to a person through their doctor, there are slightly less accurate ways of measuring body composition. For example, a process known as BIA, or bioelectrical impedance analysis. That's a fancy term for basically standing on a scale that has electrodes that run very small electric waves through your body that you can't feel, and that measures your body composition fairly accurately. This is available at most gyms or health facilities throughout the U.S. and now many physician's offices are obtaining these types of scales. You can also purchase one of these scales for your home. So it's really quite readily available and it's becoming more and more available.

Dr. Diane Reidy-Lagunes (06:56):

Talk to us about intermittent fasting and the cancer patient. Is there ever a role for that? Because that does seem to be something that there's a lot of hype going on right now for that.

Dr. Neil Iyengar (07:04):

Yeah, so this is also an area of great research and of great interest. Intermittent fasting has been found to be a successful way of losing weight for some people, not for everyone. We do know that in some folks, myself included, when you break the fast, you sometimes go a little overboard. But for other folks, it works out really quite well, and it really has to do with alignment of schedules. That being said, we're learning that the number of hours that a person fasts is directly relevant to insulin levels. We're learning how that aligns with your circadian rhythms, and your sleep patterns can also impact how efficacious or how helpful intermittent fasting is. And finally, as you so well put it Diane, the jury is still out on whether intermittent fasting is helpful from a cancer perspective. I do give folks one note of caution. For example, a recent study has shown us that intermittent fasting was no better than a self-directed diet for weight loss and in fact, folks lost muscle mass if they followed an intermittent fasting protocol. That's particularly worrisome for patients with cancer because our muscle mass is so important to maintain when we're undergoing cancer therapies.

Dr. Diane Reidy-Lagunes (08:19):

Absolutely. So tell us a little bit about the research you've done thus far. Obviously, like you said, you're doing a lot of really important work for us to better understand in years to come, but for now, have you learned a link between nutrition and cancer? And is there a role, for example, for a plant-based diet in our patients that are being treated actively for cancer?

Dr. Neil Iyengar (08:37):

Yes absolutely. I think there is a role specifically for a plant-based diet. The work that we've done over the past many years now is to first understand the biology of how the fat tissue could contribute to cancer risk and outcomes. We're learning that for a good amount, a good number of women who are at risk for the most common type of breast cancer, that there may be great benefit in reducing the amount of fat tissue and particularly in helping the fat tissue in the breast perform better. In other words, the breast is largely made up of fat tissue. In fact, if you think of most cancers – prostate cancer in men – these organs are surrounded by fat. So it doesn't take a great leap of faith to understand that the fat tissue is really relevant directly to the tumor, which is oftentimes embedded in that fat. So we hypothesized that something like the plant-based diet may be able to reduce inflammation in the fat tissue. It may reduce the amount of estrogen hormone that's being produced in the fat tissue. And all of this together may create a hostile environment for tumor growth in the breast. And this could also be exported to other cancers. We could see the same results in prostate cancer, for example, or colon cancer. And that's why I think that the preliminary data for plant-based diet is exciting because of its anti-inflammatory effects, it's pro-metabolic effects. But I will say that there are certain tumors that have genetics that may not respond to plant-based diet, or they may respond to plant-based diet, but respond better to other types of diets. So we are testing ketogenic diets as well, we're testing low carbohydrate diets as well, and ultimately I hope that this data will, again, help us with that individualized approach.

Dr. Diane Reidy-Lagunes (10:30):

Obviously you have lots of studies to help us define the best diet, potentially in a personalized way in optimal living, but the best diet today would be...

Dr. Neil Iyengar (10:41):

That's the million dollar question. So, you know, I think that I would categorize this as two different ways. One is for reducing our risk of developing cancer. So I tell folks that if you can generally maintain a normal or healthy body mass index – which is less than 25, greater than 18 – and you can maintain a healthy level of body fat – which is less than 30% – then we're likely reducing our risk of cancer. And I think, in my opinion, the best way to do this is to consume a plant-forward diet, which is high in fiber, which tends to be balanced in carbohydrate intake. It's not necessarily low carb, but it's at least balanced in carbohydrate intake so that we're not driving our insulin levels up. It has plant protein involved. If folks want to include lean meats to increase their protein intake, like fish for example, that can also be helpful in moderation. That's another key – in moderation – and following this kind of general diet with physical activity – which is at least 150 minutes of moderate-level physical activity per week – generally helps us to keep our weight in a healthy range and our body fat in a healthy range, and helps to reduce our risk for developing cancer. The second category are folks who've been diagnosed with cancer. Luckily, a lot of the same principles apply, but I think that that's also the area where we're really going to start to see that specific tumor biology may help us to refine those recommendations even further. So perhaps a ketogenic diet may be appropriate for an individual who has a very specific type of breast cancer, and we've got a clinical trial testing that right now. I would still stick with all of those general principles that I just outlined, but I think very soon we'll start to have more data to make it even more personalized.

Dr. Diane Reidy-Lagunes (12:38):

What about the other side of the spectrum, Neil? Like patients of mine, for example, with pancreas cancer and other malignancies, where it's just really hard to eat. Their appetite is diminished, they just can't seem to keep the calories on and keep that weight on. And I would imagine there's a different approach here. Any data that we have to drive what's the best approach for those patients, where they're really just trying to keep the calories in and keep the weight on?

Dr. Neil Iyengar (13:03):

Yeah that's such an important question, Diane. For the kind of patient that you outlined that is perhaps struggling to maintain nutritional intake, the priorities are a little different there. If somebody's struggling to keep even the basic level of calorie intake to maintain their body's basic processes, then the goal there is simply caloric intake. Once we get to a level where we're taking in a basic amount of calories, so that we're not dramatically losing weight, then we can start to refine it such that the macro nutrients of that caloric intake – like the carbohydrates, like the protein – are ideal for that individual so that we can maintain muscle mass and try not to gain more fat mass.

Dr. Diane Reidy-Lagunes (13:46):

Can you talk to me about how exercise is incorporated into metabolic health?

Dr. Neil Iyengar (13:51):

Exercise is such an important part of the equation when it comes to metabolic health and energy balance because that essentially is the amount of energy that we're expending or releasing. There are many beneficial effects of exercise that go beyond our weight and weight maintenance. But generally speaking, I encourage people to be physically active. We know that maintaining a level of 150 minutes per week of moderate-level activity, or 90 minutes per week of intensive activity like high intensity training, is generally beneficial in terms of helping people with side effects from cancer treatment or even symptoms from the cancer itself. And one of the things that we're researching is that exercise may actually also have direct anti-cancer benefits,

Dr. Diane Reidy-Lagunes (14:39):

You clearly practice what you preach. Can you tell us a little bit about who you are and what made you mindful of what you should eat?

Dr. Neil Iyengar (14:46):

Yeah, absolutely. So I've always had an interest in lifestyle interventions and how we may be able to modify our own cancer risk or outcomes based on what we do every day, what we eat and our physical activity and so forth. And that nicely merged with my scientific interests, which was really how various hormones – classical hormones like estrogen and testosterone, but also metabolic hormones like insulin, for example – how those molecules drive our risk of cancer. And when I was a budding medical student and learned that we can modify the levels of those hormones simply by what we do everyday, I was fascinated. And so a match was made and now I've dedicated my career to really understanding how we can use these lifestyle approaches to modifying our biology.

Dr. Diane Reidy-Lagunes (15:39):

You dedicated your life and your career to helping women with breast cancer, and then you had your own personal journey when your mom was diagnosed. Can you share a little bit of that and what that was like?

Dr. Neil Iyengar (15:51):

I'd be happy to, and thanks for raising that, Diane. I think it's helpful and important for me to talk about this because it has really informed the way that I interact with my own patients, and also the research that we do. I always say my mother is always giving, giving, giving, and, and I would have never wished this experience on her, but even with this, she's given me the insights to improve what I do in my clinical practice and in my research. And so you can imagine that having a close family relative diagnosed with cancer is scary situation, especially when you do what we do. You automatically imagine the worst because you've seen the worst. And that's how I felt when my mom was diagnosed with cancer. And we were very fortunate that she was diagnosed with a curable type of breast cancer, and that we were surrounded by my colleagues, my family – I've never seen a community come together so wonderfully as the MSK community, and that's something, as you know Diane, we do every day for our patients – and it was just so wonderful to have my mom treated by my colleagues and by my friends. Her experience helped me see the day-to-day struggles that patients go through, and it also helped us refine some of our lifestyle interventions. She actually participated, she signed up and participated for one of our exercise trials during her chemotherapy. And every day I would hear from her what works and what doesn't work. And that really has helped our research even more.

Dr. Diane Reidy-Lagunes (17:21):

Neil, in your own work to improve people's wellbeing before and after treatment, what do you think are the most important things that we can do for people? And in particular, I'm referencing your optimal living program. Can you tell us a little bit more about how that might help people and make a difference?

Dr. Neil Iyengar (17:37):

Absolutely. There's so much that we can do when it comes to our overall wellbeing, particularly in the context of a cancer diagnosis. And so in the optimal living program, we're bringing together multiple resources that address various lifestyle issues like diet, like exercise, like mental health and so forth. And we're bringing that in a personalized way to our patients at the time of cancer diagnosis. We've learned that it's so important that we address these issues right away and to carry those programs or that ability to optimize wellbeing right from the start of cancer treatment. And that may help us not only improve our overall wellbeing, but also potentially reduce the risk of long-term complications from cancer therapy and perhaps even improve response to cancer therapy. And that's what we're doing with the optimal living program.

Dr. Diane Reidy-Lagunes (18:36):

Beautiful. Okay, lastly, we had a couple of listeners call in with a couple of questions so we're just going to do this as a true or false.

Dr. Neil Iyengar (18:43):


Dr. Diane Reidy-Lagunes (18:43):

Intake of fat is bad for you, eating fat – true or false?

Dr. Neil Iyengar (18:47):


Dr. Diane Reidy-Lagunes (18:47):

False. Gluten is bad for you.

Dr. Neil Iyengar (18:53):

Oh that's a tricky question. I would say depends on the individual.

Dr. Diane Reidy-Lagunes (18:57):

That's right. Sugar is bad.

Dr. Neil Iyengar (19:00):

Also tricky question. I think I would refer to your prior podcast on that. In moderation, I would say, is the best approach.

Dr. Diane Reidy-Lagunes (19:08):

We should drink water before we eat to become more satiated.

Dr. Neil Iyengar (19:13):

For some people that works. Again, personalization.

Dr. Diane Reidy-Lagunes (19:16):

Don't eat late at night.

Dr. Neil Iyengar (19:18):

Generally that's a good principle to follow.

Dr. Diane Reidy-Lagunes (19:20):

You have to eat to lose weight.

Dr. Neil Iyengar (19:22):

Uh, yes and no. I'm sorry Diane, I'm not following your true or false.

Dr. Diane Reidy-Lagunes (19:28):

That's okay. I get it. These are tricky.

Dr. Neil Iyengar (19:30):

I think we have to eat smart in order to maintain a healthy weight.

Dr. Diane Reidy-Lagunes (19:35):

So does that include calorie counting?

Dr. Neil Iyengar (19:37):

It can. For some folks, calorie counting can be a very powerful tool. For other individuals, it causes a certain amount of anxiety. And so I often say during the first few weeks of modifying somebody's diet, it's a trial and error period where we find the right approach for that individual.

Dr. Diane Reidy-Lagunes (19:52):

Neil, you're terrific. Thank you so much for your insights. This has been very helpful.

Dr. Neil Iyengar (19:56):

Thank you so much. It was a pleasure joining you, Diane.

Dr. Diane Reidy-Lagunes (20:01):

Thank you for listening to Cancer Straight Talk from Memorial Sloan Kettering Cancer Center. For more information, or to send us any questions you have, please visit us at mskcc.org/podcast. Help other people find this helpful resource by rating and reviewing this podcast at Apple Podcasts or wherever you listen to your podcasts. I'm Dr. Diane Reidy-Lagunes. Onward and upward.