Intermittent Fasting: A Conversation with Dr. Shad Marvasti on Optimising Health

By William J. Furney

Our world is rife with confusing and often conflicting information about health and nutrition. Amid the buzz, intermittent fasting (IF) has emerged as a growing trend, intriguing health enthusiasts with its promising benefits. To clear the fog surrounding this practice and provide a clearer picture of its potential impacts, I asked Dr. Shad Marvasti, an expert on intermittent fasting and the founder and director of the Culinary Medicine Program at the University of Arizona College of Medicine, for his thoughts. 

Our in-depth conversation explores the rise of intermittent fasting, its purported health benefits, methods of incorporating it into your lifestyle and its role in addressing global health crises like obesity and associated conditions such as diabetes and heart disease. We also delve into the realm of “food as medicine” and the crucial role of dietary choices in overall health, and how these intersect with intermittent fasting.

Dr. Marvasti, who takes an holistic approach to health and wellbeing, presents a nuanced view of intermittent fasting. He tackles commonly asked questions and concerns, sharing profound insights about hunger management, eating schedules and the potential effects on energy levels, blood pressure and weight loss.

From the medical perspective, Dr. Marvasti discusses the possible impacts of IF on our bodies at the cellular level, like autophagy (the body’s way of cleaning out damaged cells to regenerate healthier ones) and oxidative stress (a primary driver of age-related degeneration and disease). He shares his recommendations for types of IF and its integration into various lifestyles, including physically active individuals.

Dr. Marvasti doesn’t shy away from addressing the hard questions either. We explore societal influence, the role of Big Food and Big Pharma in health problems today and potential risks associated with intermittent fasting, such as the development of eating disorders.

Dr. Marvasti also shares inspiring success stories from his patients who have benefited from incorporating intermittent fasting into their lifestyle.

Real Food as Medicine: Dr. Shad Marvasti. 

Why do you think intermittent fasting has become so popular in recent times?

I think intermittent fasting has become popular because it has a variety of health benefits. Although various forms of fasting have been around for thousands of years, it’s only in the last decade that we’re beginning to see modern medical scientific evidence to support its benefits for health. One other reason for its popularity is that it doesn’t involve major changes to one’s diet and really is about restricting the timing of when you eat during a 24 hour day. 

What are the actual benefits of IF, that someone doing it for a short time — say a few weeks — might notice?

Some benefits that people will begin to notice is surprisingly more energy during the fasting time. Also, patients may begin to see lower blood pressure and also start to lose weight as well. 

Obviously many people starting out with a fasting regime are concerned about hunger pangs. What can you do to prevent them? And should people fear hunger? 

The best is to start with a shorter fasting window and also make sure to add in healthy fats to the time you are eating. This helps to control appetite. The fasting process itself will also, surprisingly, result in less hunger over time during the fasting window as your body will adapt to the new schedule. Many times we confuse thirst for hunger, so when you’re hungry between meals or during a fasting period, it’s important to drink plenty of water. 

Intermittent fasting has already been shown to decrease blood sugar and all the other major risk factors for heart disease, including cholesterol, high blood pressure and excess weight.

Dr. Shad Marvasti

The global obesity crisis and its profound health problems, such as diabetes and heart disease, shows that people are eating far too much, and mostly of the wrong types of food and drinks — highly processed, lots of sugar, the wrong types of fats. Coupled with mostly sedentary lives. Might IF be a solution to this?

Yes IF may be a potential solution as it gives our bodies “metabolic rest” from digesting and processing food. This will naturally result in some shrinking of our stomach and reduced portion sizes when we do eat. Also, if we restrict eating to daylight hours and avoid any food at night, this will also help to reduce weight. Intermittent fasting has already been shown to decrease blood sugar and all the other major risk factors for heart disease, including cholesterol, high blood pressure and excess weight. 

You say your “goal is to empower you to achieve optimal health in all aspects of life”. Is IF a way to achieve someone’s best possible health condition?

IF is definitely one path to achieving optimal health as it boosts our body’s ability to heal itself by giving it the time and space it needs to do so. Fasting has been shown to result in increased autophagy or destruction of metabolic debris in our bodies. This metabolic debris may include early cancer cells or inflammatory cells that lead to narrowing of the arteries. When the body is given the chance to rest from the work of digestion, it can work on repairing itself and at the cellular level slow down the process of wear and tear — termed oxidative stress — that is the cause of premature ageing.  

Medical experts seem to disagree on when the body enters autophagy during fasting. After how many hours do you think it begins?

I think the sweet spot is after 14 hours, so that’s why I recommend at least 16 hours of fasting. I would work up to this as you are adjusting and discuss with your doctor, especially if you have any ongoing medical conditions or are taking medications.  

You founded the Culinary Medicine Program at the University of Arizona, based on the premise that “food is medicine” — what kind of foods, and which are best? Is a vegan diet better than one that’s heavy on red meat, for example? 

First of all, I believe that we have to begin by eating real food. Real food is food that is not highly processed and mostly food that comes out of the ground. The Standard American Diet is sad, with nearly 70% processed foods that are now being linked directly to cancer, heart disease, diabetes and obesity.  

In general, you can’t go wrong with eating a plant-forward diet. If you do eat meat, you want it to be meat that is not processed or loaded up with hormones and antibiotics, leading to a variety of health consequences for humans. 

I think another key for our diet is healthy fat for a healthy heart and brain and mood. For far too long, fat had been demonised and replaced with simple carbs and sugars. Healthy fats like monounsaturated fats found in extra virgin olive oil and avocados can literally make us thin and lower our risk for heart disease, diabetes and dementia.  We can also benefit from fibre, which is the main food source for the microbiome. 

When the body is given the chance to rest from the work of digestion, it can work on repairing itself and at the cellular level.

Dr. Shad Marvasti

Is the food industry, and its advertising, along with “Big Pharma”, responsible for many of the health problems today? And, if so, what can be done about it? Do both really want people to be addicted to bad food and being unhealthy, so they’re reliant on medications — all for profit?

I think there are unfortunately many parallels between Big Food and Big Tobacco. The processed foods with many flavours that have no accompanying nutrients have hijacked our taste buds and pushed us into an endless cycle of cravings that result in high calorie, low nutrient foods.  

We vote one bite at a time with the food we eat, so if we all changed our food and supported local farmers’ markets, I think we could start to change this. We also need to advocate for policy changes that make healthy, real food options inexpensive and widely available. Our current food system is broken and our food policies favour the production of cheap and widely available processed foods that are literally making us sick.  

I do believe in food as medicine and I also prescribe medications when needed. I don’t use medication to replace a diet or lifestyle changes. In many cases, if we make the diet and lifestyle changes, as many of my patients do, we can wean off many medications and not rely on them forever. Food is a much better source of medicine, without as many potential side-effects.  

The incentives are not aligned right now but I think that is changing as we are beginning to recognise that diet is the number one risk factor for preventable disease and premature death.  That’s why I am involved in redesigning medical education to train future doctors to give food and lifestyle prescriptions in addition to considering medications and other procedures if necessary. 

There are several types of IF — 16:8, 18:6 and so on. Which do you recommend? Which is most effective? 

I think working your way up to 16:8, where you don’t eat anything past sunset avoiding nighttime eating, which is associated with insulin resistance and weight gain, is best and most effective — based on my reading of the evidence to date.  

Is IF something you should incorporate into your life and do daily, or only for a short spell? 

I think it’s something you want to work on incorporating into your life; but as with any new lifestyle change, you should biohack yourself and experiment to see what works for you.  

Do you recommend IF for people who may not have weight issues?

Yes, because I think it can still have other health benefits. 

Can you do IF and still eat junk food, if you want to be healthy? 

I don’t think you can have your cake and eat it too. IF is a good start, and perhaps you can transition from there to eating real food as that’s the ultimate goal. 

Can you eat as much as you want within your eating window, or do you still have to be careful?

I think you can eat as much as you feel your body needs — provided you are hydrating yourself and are not overeating. One tip that long-lived cultures do is to eat until you are 80% full, instead of eating more. We know from all the research that any form of calorie restriction can contribute to longevity, so that’s helpful. However, I wouldn’t focus on calories but rather on the quality of the food that you eat, making sure it’s not processed and is real food. 

Our current food system is broken and our food policies favour the production of cheap and widely available processed foods that are literally making us sick.

Dr. Shad Marvasti

What about people who are physically active, like those who do a lot of working out and sports? Can they do IF or not?

Yes. In fact, if you work out at the end of your fasting period you will boost the health benefits and increase autophagy, which is one of the main reasons why fasting is good for health and longevity. Make sure to stay hydrated as that’s key.  

How long does it take for IF to work, if you’re seeking to shed some pounds?

I would say a few months are important to get acclimated and work your way up to a longer fasting period. 

Longer fasting periods appear to be getting more popular — like 12, 24 and three-day fasts. What’s your view of those, including even longer “water fasts”?

I think these can be useful, with caution, to see how you feel and again to speak with your doctor, especially if you’re taking medications. The evidence does show that this can reduce inflammatory markers associated with premature ageing, so it’s something to try once or twice a month. 

Is there a risk that IF can lead to eating disorders, as some people have suggested?

It can if you overly focus on the negative side, instead of having the right mindset about it.  It’s important to think of it as giving your body water and rest from food for a number of hours during the fast.  

What are some of the IF success stories you’ve seen? 

I’ve seen patients control their diabetes and decrease or completely get off their medications. I’ve seen patients with high cholesterol no longer need medications for this. I’ve seen patients with high blood pressure have much lower bp medication dosages or also go off their medications completely with this. And I’ve also seen patients lose weight, especially when changing their diet to avoid processed foods along with intermittent fasting. 

  • Title image courtesy the University of Arizona College of Medicine.

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