Are you intermittent fasting the wrong way? Many people focus on how long they fast—but according to nutrition scientist and science communicator Melanie Murphy of L-Nutra, when you eat may matter just as much. In this episode of Six Weeks to Fitness, Vince Ferguson talks with Melanie about intermittent fasting, circadian rhythm, fasting after 40, protein intake, metabolic health, the Fasting Mimicking Diet, Prolon, muscle preservation, sleep, longevity and healthspan. Melanie explains why some popular intermittent fasting schedules may work against the body’s natural circadian rhythm and why eating late in the day can be very different from eating earlier. She also discusses why breakfast may be more important than many people think and what people should understand before adopting a fasting routine.

But fasting isn’t the only controversial topic we tackle. Are some people consuming too much protein in the pursuit of muscle and better health? What happens inside the body during a fast? What is autophagy? Can you get some of the benefits associated with fasting while still eating? And how does the Fasting Mimicking Diet differ from traditional water fasting? Melanie also discusses the research behind fasting and metabolic health, the importance of protecting muscle as we age, why sleep is one of her personal non-negotiables, and why healthspan—not simply lifespan—should be part of the longevity conversation. Vince also shares his own experience trying the Prolon 5-Day Fasting Mimicking Diet.

If you’re over 40 and interested in intermittent fasting, healthy aging, nutrition, metabolic health, maintaining muscle, longevity and adding more life to your years, this conversation will give you plenty to think about. Topics discussed include: intermittent fasting • fasting after 40 • circadian rhythm • fasting mistakes • meal timing • protein intake • metabolic health • autophagy • Prolon • Fasting Mimicking Diet • L-Nutra • muscle preservation • healthy aging • longevity • healthspan • sleep • nutrition after 40

If you find this conversation helpful, like the video, subscribe to Six Weeks to Fitness, and share it with someone who is interested in fasting, nutrition and healthy aging.

Full Episode Transcript

Interview with Melanie Murphy of L-Nutra

Meet Melanie Murphy

How Much Control Do We Have Over How We Age?

Vince Ferguson: We hear a lot today about longevity – living longer, slowing aging and extending healthspan. But what does any of this actually mean for someone in their 40s, 50s or 60s who simply wants to live better, stay strong and remain healthy as they get older? My guest is Melanie Murphy, a nutrition scientist and science communicator who teaches nutrition physiology at UC Irvine. She is also co-host of the Almost Forever podcast and works with L-Nutra, the company behind Prolon and the Fasting Mimicking Diet. Melanie, thank you for coming on the show. How are you?

Melanie Murphy: Thank you so much for having me. It’s a pleasure.

Vince Ferguson: Let me start with something I think a lot of people over 40 wonder about: How much control do we really have over how we age?

Melanie Murphy: So much. We have so much control over how we age. I don’t want to quote an exact statistic without checking it, but genetics plays a significantly smaller role than we once thought in how our health evolves over time. So much of our diet, environment and what we consume – not only food and drink, but emotionally and mentally – plays a huge role in whether or not our genes are expressed. We might be born with a specific set of DNA, and heart disease or diabetes might run in the family, but diet, lifestyle and exercise can influence how those genes are expressed.

Vince Ferguson: Most people look at someone who is living a long life or aging well and think, “It must be genetics.”

Melanie Murphy: There can absolutely be a genetic component. We see people who have a great diet, exercise, lift weights and do everything they are supposed to do, yet still have high LDL or high cholesterol. Genetics can be at play. But a predisposition does not mean you are bound for that disease or illness. If we understand how our bodies react to certain foods and how our health is being expressed, we can influence our health trajectory.

Vince Ferguson: That tells me there’s hope.

Melanie Murphy: So much hope. I find that empowering, although for some people it can also feel overwhelming. One of the things we try to do on our podcast and at L-Nutra is give people actionable ways to improve their health so it doesn’t feel like, “I have all this control, but I don’t know where to begin.”

Are People Fasting the Wrong Way?

Vince Ferguson: From your perspective, what is something people over 40 may be doing every day that works against healthy aging?

Melanie Murphy: There are a few trending things that I think can be detrimental, especially for women over 40 and 50. One is that a lot of people are intermittent fasting incorrectly. Intermittent fasting can have wonderful benefits for things like blood glucose and body composition. But many people hear “intermittent fasting” and think they should skip breakfast, start eating at 1:00 p.m. and finish at 9:00 p.m.

Melanie Murphy: That can completely bypass the natural circadian rhythm our bodies work within. If you’re shortening your eating window, start your day with breakfast and stop eating earlier. Follow the patterns of the sun: eat within the first hour or two of waking and ideally stop eating three or four hours before bed. For many people that might look like eating around 8:00 a.m. and finishing around 6:00 p.m. A lot of people are doing that backwards, which can raise cortisol, contribute to chronic inflammation and affect hormones, especially in women. It doesn’t mean intermittent fasting is bad; it means a lot of people are doing it the wrong way.

The Protein Conversation: More Is Not Always Better

Vince Ferguson: What else comes to mind?

Melanie Murphy: The protein trend is an interesting one to unpack. I love that protein is having a moment because amino acids, the building blocks of protein, are needed for virtually every physical process in the body. Protein is incredibly important. But a lot of people are thinking only about sheer quantity rather than the types of protein they consume and how much they actually need based on their health status and stage of life.

Melanie Murphy: This one-gram-per-pound protein trend can cause more harm than good from a health perspective. Too much protein can trigger mechanisms in the body that promote growth. That is part of why people consume it – they want to grow muscle and change body composition. But triggering growth pathways too frequently can also accelerate cell growth, meaning our cells may age faster than we want them to.

Melanie Murphy: We absolutely need enough protein, but it isn’t only about the number of grams. Quality matters. Plant-based proteins such as legumes, tofu and beans can provide the protein the body needs while fitting into a healthy-aging approach. The right amount is personalized. People are getting parts of the protein conversation wrong.

What Happens in the Body During a Fast?

Vince Ferguson: What is actually happening in our bodies when we fast, and why has fasting become such an important part of the longevity conversation?

Melanie Murphy: It is a critically missing component for a lot of people. First, intermittent fasting or time-restricted eating is different from a prolonged fast. Prolonged fasting generally means three days or more, and in our work a five-day period is particularly important because of the mechanisms it can activate.

Melanie Murphy: One of those mechanisms is autophagy. When calories and nutrients are sufficiently restricted, the body enters a protective state. Cells begin cleaning up damaged or dying cellular components and using some of that material for energy. When food is reintroduced, cells can rebuild functioning components using new nutrients. I sometimes describe autophagy as the first step in cleaning up the cellular “sludge” we naturally produce over time.

Melanie Murphy: Everyone produces cellular debris as cells multiply and divide. Historically, humans also experienced periods when food wasn’t constantly available. Today, many of us eat throughout the day and rarely have those longer periods of restriction. Certain religious traditions still incorporate fasting, but for many people that pattern is absent.

Vince Ferguson: So fasting plays a vital part in the longevity equation?

Melanie Murphy: I think it is a missing piece in the longevity equation. At L-Nutra, our work on the Fasting Mimicking Diet has examined fasting across multiple systems. The idea is that fasting doesn’t address only one marker; it can affect areas such as visceral fat, glucose regulation, gut health, brain health, skin health and cognitive clarity. That multi-system effect is what makes it so interesting.

How Can You Mimic Fasting While Still Eating?

Vince Ferguson: For someone hearing “Fasting Mimicking Diet” for the first time, how can you mimic fasting while still eating food?

Melanie Murphy: It sounds counterintuitive, right? Sometimes I wish the word “fasting” wasn’t in the name because it isn’t fasting in the traditional sense. Dr. Valter Longo, who founded L-Nutra, studied fasting and cellular-rejuvenation pathways. Part of the challenge was finding a way to activate fasting-related mechanisms without completely depriving people of nutrients.

Melanie Murphy: The research focused on nutrient-sensing pathways, including mTOR, IGF-1 and PKA. The idea is that the body has thresholds for nutrients. It isn’t as simple as eating one slice of apple and suddenly switching every nutrient sensor on. The amounts and ratios of carbohydrates, protein and fat matter.

Melanie Murphy: The Fasting Mimicking Diet was designed around a specific ratio of nutrients that provides food while remaining below certain nutrient-sensing thresholds. You eat breakfast, lunch and dinner, including foods such as nut bars and plant-based soups, and even dessert on some days. The goal is to provide nutrients while still encouraging fasting-related cellular processes during the five-day program.

Vince Ferguson: I’ve tried the Fasting Mimicking Diet. What surprised me was that I was able to eat the products and wasn’t really hungry. I also noticed mental clarity and lost a few pounds even though weight loss wasn’t my goal. I’m not endorsing it simply because I used it, but I had a good experience. How can you consume calories and still obtain those fasting-related effects?

Melanie Murphy: That goes back to the specific nutrient ratios and thresholds. It’s also worth recognizing that the standard advice – change your diet every day and exercise – works in theory, but implementing it consistently can be difficult. People have stress, children, full-time jobs and sometimes multiple jobs. It isn’t easy to cook every meal at home and maintain a perfect exercise schedule.

Melanie Murphy: The FMD is designed as a five-day intervention. For someone starting the program, our general recommendation is once a month for at least three months and then approximately quarterly, depending on the individual. In our studies we track outcomes such as visceral fat, glucose, insulin sensitivity, blood pressure and cholesterol markers. The goal is an intervention that meets people where they are.

Melanie Murphy: We also studied the FMD against a Mediterranean-diet intervention over several months. The point of that comparison was time: can a short, structured intervention produce meaningful metabolic changes for people who struggle to overhaul every day of their lives? That is the practical problem we are trying to address.

Who Should – and Should Not – Fast?

Vince Ferguson: Is fasting for everybody? Can anyone fast?

Melanie Murphy: If we’re talking specifically about the FMD, most otherwise healthy people can follow it. A water-only fast is different. We would not recommend someone with diabetes, heart disease or another preexisting condition undertake a prolonged water-only fast on their own. The FMD is food-based and designed differently.

Melanie Murphy: Even with the FMD, if you have a preexisting condition or take medication, talk with your healthcare practitioner first. There can be medication considerations. For example, someone taking a GLP-1 may need individualized guidance because of overlapping effects on glucose. It is important for a clinician to know what you’re doing.

Vince Ferguson: So you’re not starving yourself?

Melanie Murphy: Correct. You are eating food for five days.

Vince Ferguson: And after those five days, can someone simply go back to eating the way they were?

Melanie Murphy: As a dietitian, I’m never going to say that what you do day in and day out doesn’t matter. Reducing excess sugar, getting adequate nourishing protein, healthy fats and enough fiber all matter. Healthy habits between cycles can support and potentially enhance the benefits. But our clinical trials are focused on the intervention itself rather than requiring people to follow a perfect lifestyle between cycles.

Food as Information – and Protecting Muscle

Vince Ferguson: So you’re basically feeding the body on a cellular level?

Melanie Murphy: Yes. You’re giving your cells information that helps trigger certain mechanisms. I wouldn’t call it a biohack; it is a very precise way of giving the body information that can activate mechanisms it already has.

Vince Ferguson: I often talk about cells communicating with each other. Food is information.

Melanie Murphy: Exactly. And sometimes the information isn’t good. A typical Western diet can repeatedly signal the body in ways we don’t want – for example, constantly pushing insulin demand or growth pathways. Nutrition is one of the primary ways we can intervene in that process rather than continually giving the body excess sugar, saturated fat and other inputs associated with poor health.

Vince Ferguson: As we get older, muscle becomes even more important. What does the Fasting Mimicking Diet mean for muscle, and can someone still exercise?

Melanie Murphy: The program includes specific amounts of protein and glucose. In our studies, we have seen muscle protection while targeting visceral fat, the dangerous fat around the organs. During the five days, however, we don’t recommend a lot of strenuous physical activity. Fasting is already a stressor on the body, even when it is a more nourishing version of a fast.

Melanie Murphy: Exercise is also a beneficial form of stress, but stacking hard training on top of fasting can be a lot, especially if you are new to the program. We don’t recommend HIIT workouts or marathon training during those five days. Walking, stretching or gentle yoga can feel good. Afterward, people can return to their normal training.

Vince Ferguson: When I did the program, I exercised, but not every day and not at full intensity. I probably worked at about 50 percent of my normal ability. That worked for me, although it may not be right for everyone.

Melanie Murphy: And that brings up something important: people who are very fitness-focused sometimes forget how important rest periods are. Five days is not a long time. Rest is not necessarily a step backward from your routine; it can be another layer of the routine – rest and repair.

Community, Coaching and the Bigger Longevity Picture

Vince Ferguson: I remember there being some type of coaching program when I used it. Can you explain that?

Melanie Murphy: During FMD weeks, group coaching is available with longevity-trained dietitians. Participants can learn what may be happening in the body that day, get practical tips for common challenges such as fatigue, ask questions and connect with other people doing the program. I think one of the best ways to succeed with a fast is to do it with somebody or have a community around you.

Melanie Murphy: We are also building a broader longevity program that goes beyond nutrition and exercise into stress, relationships, sleep and other parts of the longevity ecosystem, along with tools for tracking lifestyle and biometric information.

The Health Habit Melanie Won’t Compromise On

Vince Ferguson: Knowing everything you know today about longevity and nutrition, what is one thing you consistently do now that you weren’t doing 10 years ago?

Melanie Murphy: The FMD would be an easy answer because I started incorporating it in 2018, but I’ll give you another one: sleep. I will not compromise on sleep anymore. It makes too big an impact on a day-to-day basis. Some days I’ll go to sleep at [8:30] and sleep until [7:00] if that is what my body needs.

Melanie Murphy: If you compromise on sleep, it can affect you long-term. It affects stress levels, circadian rhythm, gut health and digestion. There are so many downstream effects of not getting good sleep that, at this point in my life, sleep is non-negotiable.

Vince Ferguson: So you’re not one of those people who says, “Five or six hours and I’m good”?

Melanie Murphy: No. There may be a small population that functions well with very little sleep, but I don’t think the vast majority of us do. Women especially can feel pressure to push, push, push because so much is expected at the family and career level. Sleep becomes, “I don’t have time for that.” I think that mindset can be detrimental. From the brain to the gut to glucose levels and digestion, sleep patterns affect so much. I will absolutely die on the sleep pillow: get more sleep.

Melanie Murphy: And go slower. We all need to go slower in our everyday lives. We’re moving way too fast.

Vince Ferguson: I’ve come to realize how important sleep is, too. I used to think, “If I get six hours, I’m great.” But if I get seven, I’m fantastic.

Melanie Murphy: Why go 80 percent when you can go 100 percent?

Almost Forever: Cutting Through Longevity Noise

Vince Ferguson: You co-host the Almost Forever podcast with Renee Fitton. What are you hoping to bring to the longevity conversation that people aren’t getting elsewhere?

Melanie Murphy: There is so much noise around nutrition and longevity. Many people get nutrition and longevity information from people who are not credentialed and don’t have a research or educational background in the advice they’re giving. We think that can be dangerous and confusing, especially because the science is constantly evolving.

Melanie Murphy: We wanted to create a place where people can get accurate, science-backed information from credentialed professionals who are doing the research and can discuss findings that may differ from trends on social media or the internet.

Melanie Murphy: Something else that is near and dear to my heart is that so many longevity conversations are led by men. There aren’t as many women taking up space in this field and bringing a different set of eyes, ears and experiences. Renee and I want women to be part of leading that conversation, too. We have fun with it. We take nutrition trends and look at the science and data to ask whether something is a myth or a method, and we involve our audience by answering their questions.

Vince Ferguson: I’m all about healthspan. I want to live almost forever, but I want to be able to get out of a chair on my own, get down on the floor and play with the kids. I want to be healthy.

Melanie Murphy: Exactly. We want you to live in your most vibrant body for as long as possible. Imagine what we could accomplish if we weren’t bogged down by a body that isn’t functioning well or constantly managing disease. You don’t have to be riddled with age-related disease simply because you reach a particular age. It doesn’t have to be your destiny.

Where the Research Is Going

Vince Ferguson: You’ve also talked about heart health and people dealing with high blood pressure. What areas are you studying?

Melanie Murphy: Heart health is one of the markers we regularly track, and we have studied cardiovascular-related outcomes extensively with the FMD. We also look at diabetes and weight care, including losing fat while protecting muscle. Some of our newer research is exploring autoimmune conditions, including Crohn’s disease, as well as cancer. We’re expanding the research in a big way.

Where to Learn More

Vince Ferguson: For people who want to learn more about your podcast, L-Nutra or Prolon, where should they go?

Melanie Murphy: If you are otherwise healthy and want to learn about Prolon, you can go to ProlonLife.com. There is information about the FMD, group coaching and educational content. You can also find Prolon on social media. People with preexisting conditions who need more personalized care should work with their healthcare team and can learn about L-Nutra’s medically supervised programs. Almost Forever is available wherever you get your podcasts, including Apple Podcasts and YouTube. My personal social account is Health N Mellness – “Health,” the letter N, and “Mellness.”

One Thing to Add More Life to Your Years

Vince Ferguson: I have one final question that I ask all my guests when it comes to healthspan. If someone watching or listening today could change just one thing this week to add more life to their years, what would you tell them to do?

Melanie Murphy: This may be an unexpected answer, but prioritize your joy. Do something today that brings you unabashed joy, and be diligent about making sure every day has some of that. Health and wellness messaging can make it feel like you have to restrict, power through and keep adding more things to your plate. It can become incredibly overwhelming.

Melanie Murphy: Joy can be cooking, gardening, rollerblading, painting – whatever brings you joy and helps calm your nervous system. I think a lot of us are moving too quickly and forgetting that joy is why we’re all here. I’m not here to add more to your plate. I’m here to tell you to have a little more fun.

Vince Ferguson: I love it. Melanie, I really appreciate the work you’re doing to make longevity science understandable and help connect the dots for people.

Melanie Murphy: Thank you, and thank you for spreading the word. We’re grateful to have shows like yours that help connect the dots for people.

Vince Ferguson: And to everyone watching or listening, thank you for joining us on Six Weeks to Fitness. If you enjoyed this conversation, please like, comment, subscribe and share it with someone who could benefit. Until next time, stay healthy, stay strong and keep adding more life to your years.