Since 2017, Dr. Cecily Anne Clark-Ganheart, MD, FACOG has lost over 55 pounds and improved almost every biomarker related to insulin resistance. Her secret? Intermittent fasting.

Even as a physician in the field of maternal-fetal medicine and obesity medicine, Dr. Clark-Ganheart didn’t truly appreciate the impact that addressing insulin resistance and metabolic dysfunction could have on her health until she discovered the practice and community around intermittent fasting.

“I got into fasting about 18 months ago, when I came across The Obesity Code by Jason Fung,” Clark-Ganheart said. “At the time, I was struggling with my weight, which was my primary interest in intermittent fasting at first. I weighed almost 200 pounds when I first heard of intermittent fasting, and by the time I read The Obesity Code I was already up to around 230 pounds, so I was trending in the wrong direction. But what really got my attention was reading about the mechanisms of insulin resistance and the importance of allowing your insulin levels to come down to access and burn stored fat.”

Dr. Cecily A. Clark-Ganheart, in her office.

Chronically high insulin levels, which often accompany obesity and insulin resistance, can lead to a wide range of health problems including further weight gain, diabetes, heart disease, nonalcoholic fatty liver disease, depression, Alzheimer’s disease, asthma, some cancers and aging. One powerful way to reduce insulin levels, at least transiently, is through intermittent fasting.

“Insulin is the single most dominant hormone that promotes energy storage as fat while inhibiting energy consumption via catabolism, including lipolysis and fat oxidation.” – Insulin and insulin signaling play a critical role in fat induction of insulin resistance in mouse, 2011

Fasting for 12 to 16 hours depletes liver glycogen stores and prompts the body to enter ketosis, or fat-burning mode. Without an influx of calories, particularly carbohydrates, insulin levels also begin to drop. A previous study of prolonged fasting in humans has shown plasma insulin* to decrease by approximately 50% between 12 hours and and 72 hours of fasting, with most of this decline happening in the first 24 hours of fasting.

*Plasma insulin is the concentration of insulin in the blood; insulin is a peptide hormone that facilitates glucose uptake into cells from the blood. Chronically high levels of insulin, for example in response to added sugar intake, can lead to insulin resistance or a resistance of cells and tissues to take up insulin. This in turn leads to damagingly high levels of plasma glucose and insulin.

Shortly after reading The Obesity Code, Clark-Ganheart started her journey with intermittent fasting, a journey that continues to this day.

“I quickly noticed that I felt better and that I was also losing weight,” Clark-Ganheart said.

Over the course of 18 months, Clark-Ganheart reversed her prediabetes and was able to come off of her hypertension medication, in consultation with her primary care physician. Before her journey with intermittent fasting, she required a daily dose of 90 mg of Nifedipine XL for control of her blood pressure. Today, she is medication free with a blood pressure around 124 over 77. She also says that she has more energy than before she started fasting, and has eliminated knee and other joint pains that plagued her when she was heavier.

“I continue to lose weight and I’m still refining my diet to live healthier,” Clark-Ganheart said. “But intermittent fasting continues to be an important part of my health journey.”

Clark-Ganheart, before and after her weight loss journey with IF.

Clark-Ganheart, after and before her weight loss journey with IF.

In order to track her fasting windows and monitor her progress, Clark-Ganheart uses the LIFE Fasting Tracker app by LifeOmic. She started using the app around six months ago. Today, she and her husband have a LIFE Circle in which they fast together.

Finding a Groove with Intermittent Fasting

After reading The Obesity Code, Clark-Ganheart started, perhaps unlike most, by diving headlong into alternate day fasting and prolonged fasting, or fasting for 36 to 48 hours at a time. While this probably helped kickstart her weight loss, over time she has settled into what is for many a more sustainable pattern of time-restricted eating or an 18:6 fasting schedule. This schedule involves eating for 6 hours per day and fasting for 18, typically starting in the early evenings for Clark-Ganheart.

While she has settled into a time-restricted eating pattern, Clark-Ganheart also still practices an occasional, often monthly, 48-hour water fast. She does this primarily with the goal of kickstarting autophagy in her body, a process of cellular recycling and renewal. However, she likes to stress to her patients and the people who follow her health-based Instagram account (@fastingworkgirl) that practicing these prolonged fasts is not necessary to obtain the weight loss and metabolic health benefits of fasting.

“I think a lot of people new to fasting get intimidated, thinking these long fasts are something they have to do to get results,” Clark-Ganheart said. “I see lots of people getting great results with one-meal-a-day (OMAD) and time-restricted eating on a 16:8 or 18:6 fasting schedule. There are so many ways to fast with great benefits – even people who start with a 12-hour daily eating period often report noticing positive health results. Anything you can do to break up constant food grazing is going to be healthy, to give your body a break [from insulin signaling].”

Clark-Ganheart also noticed that her diet slowly started to change as she practiced intermittent fasting, particularly when she settled into a daily 18:6 schedule. Intermittent fasting was a gateway of sorts that led her down a path of wanting to eat better and learn more about nutrition and metabolic health more broadly.

This trend is not foreign to those who engage in intermittent fasting, and is a story commonly encountered within the fasting community online. People new to intermittent fasting often describe developing a very different relationship to both their sensations of hunger and to the food they eat when they aren’t fasting. They become more aware of what they are putting into their bodies. They might even realize for the first time that eating can be fun, not something they are doing mindlessly and constantly all day long, in the car and in front of the TV.

“By the time you have fasted 24 hours, […] you don’t want to eat a bag of Doritos. You want something good, substantial, a steak, some really nice salad or pasta,” LifeOmic CEO Don Brown recently told a reporter at the IndyStar. “You develop a different relationship with food. You might find that you eat more mindfully. You really savor every bite.”

After reading The Obesity Code, Clark-Ganheart dove into the book Deep Nutrition by Dr. Cate Shanahan. She learned about the benefits of a whole foods, more natural way of eating. She began to minimize her carbs and processed foods while increasing her intake of fruits and vegetables. Today, Clark-Ganheart emphasizes to her own patients and others that fasting isn’t an excuse to eat ‘junk’.

Learning more about plant-based nutrition and intermittent fasting.
Learning more about plant-based nutrition and intermittent fasting.

“I think you are defeating the purpose of fasting if you go on a sugar bender after a 24-hour water fast,” she said. “I think focusing on food timing and quality go hand-in-hand. Personally, I think when you focus on both of these aspects is when you are going to see the best health results overall, not just in terms of weight loss but also other health conditions.”

Today, Clark-Ganheart aims for plant-based, low-carb eating in conjunction with her daily intermittent fasting. But both within and outside of her own medical practice, she recommends that others find the nutrition and meal timing pattern that is most palatable and sustainable for them personally and that makes them feel their best.

“No matter what nutrition camp you are in, whether keto or low-carb or vegetarian, these ways of eating all have one underlying characteristic in common – they minimize processed foods. I’m also in the camp that believes that eating vegetables and fruits is never going to be bad for you. Nobody has diabetes because they ate too much broccoli. I think it’s the food made in labs and factories, the processed foods with added sugars, that are really detrimental to your health. When I talk to my patients, I primarily try to help them figure out where and how they can increase their servings of vegetables.”

Clark-Ganheart in an "after" photo on her weight loss journey with IF.
Clark-Ganheart in an “after” photo on her weight loss journey with IF.

Fasting in the Clinic

As intermittent fasting becomes an increasingly popular lifestyle health intervention, physicians, dietitians and health coaches will likely have more and more of their patients and clients come to them with questions about fasting and how it fits with their health histories, nutrition patterns, treatment plans and medications.

“Our patients are showing a lot of interest in using intermittent fasting, and many of them use the LIFE Fasting Tracker app to time their fasting windows [usually 12 to 16 hours] before their radiation treatments,” said LJ Amaral, a Research and Clinical Registered Dietitian at the Cedars-Sinai Samuel Oschin Cancer Center.

Amaral first learned about intermittent fasting in the context of cancer treatment from a conference talk she attended by Dr. Valter Longo a few years ago. She started practicing fasting herself, finding that it helped her inflammation and arthritis-related back pain. Today, Amaral supports intermittent fasting as a dietary option, along with a balanced and healthy diet, with some of the cancer patients she works with at Cedars-Sinai. Her recommendations when it comes to fasting with cancer, however, depend on individual factors including a patient’s current weight and treatment plan. She also believes that any cancer patient fasting through radiation or chemotherapy should be regimented about their fasting schedule and pair it with proper nutrition and consultation with their oncologists and dietitians, in order to maintain a healthy weight and meet their nutritional needs. The LIFE Fasting Tracker may help with this, she says, allowing physicians to monitor a patient’s fasting schedule and associated outcomes.

“It’s tricky, because we don’t want to be encouraging all cancer patients to fast,” Amaral said. “Too rapid of weight loss can lead to poor outcomes for cancer patients. But I think it’s something to consider if you are going through treatment where you aren’t having any nutrition-related side effects and are feeling well, if you have the stores or body fat reserves to do so, and if you are monitoring how long you are fasting for. I’ve seen good success so far for the patients who fast in conjunction with their radiation treatments, where they will fast for about 13-16 hours prior to radiation. However, I highly encourage patients to do their own research, to discuss their plans with their care team, and to be cautious about oncology nutrition advice they see online.”

Consult your care team and a registered dietitian for personalized nutrition advice that fits your health condition.
Consult your care team and a registered dietitian for personalized nutrition advice that fits your health conditions.

Clark-Ganheart’s own knowledge of intermittent fasting has also affected the health recommendations she makes for the patients she sees in her maternal-fetal medicine practice. Clark-Ganheart specializes in treating patients with or at risk for high-risk pregnancies. Fasting as a health practice is contraindicated for pregnant and lactating women, but Dr. Clark-Ganheart sees many patients who come back to her after birth for help with postpartum weight loss, as well as patients who need help with preconception weight loss.

“I find that a lot of the common mechanisms of obesity also predispose people to poor pregnancy outcomes,” Clark-Ganheart said. “In that setting, we definitely suggest intermittent fasting as one intervention that can help. We also provide guidelines for how a woman should dial back her intermittent fasting or time-restricted eating schedule if she does become pregnant. I see a lot of women who are using intermittent fasting to manage polycystic ovary syndrome, who may have trouble dialing back when they become pregnant. If you are accustomed to intermittent fasting and you are having a busy day, it’s not uncommon to look down at your watch and realized it’s 2pm and you haven’t eaten anything!”

There is some evidence that regular prolonged fasting can have detrimental effects on a growing fetus. (Much of this research has been done in the context of Ramadan fasting.) However, in this context prolonged fasting is defined as anywhere from 12 to 18 hours, Clark-Ganheart said. So she doesn’t recommend that her patients who are pregnant eating on a clock or force themselves to eat when they aren’t hungry. But she does advise them not to go longer than 12 or so hours between meals during pregnancy, even if that means consuming something very light. Conditions such as hyperemesis [a severe type of nausea and vomiting during pregnancy] can be exacerbated by infrequent eating. It is particularly important that women listen to their bodies, prioritize the consumption of nutrient-dense foods and avoid fasting during pregnancy.

But apart from pregnant and lactating women or people with type 1 diabetes, intermittent fasting and particularly time-restricted eating are likely to be safe and to deliver health benefits in terms of weight loss and improved biomarkers of insulin sensitivity and cardiovascular health (like reduced blood pressure, lowered insulin levels, lowered fasting glucose levels, lowered levels of inflammation). However, prior to initiating fasting (or other lifestyle changes), it is important to review your specific medical conditions with your healthcare provider, especially when medications are involved.  

“I hope that in the future more people, including physicians, will be open-minded about incorporating intermittent fasting into a healthy lifestyle,” Clark-Ganheart said. “There are still so many physicians and fitness trainers who are giving the advice to eat every 2-3 hours, or to ‘eat more to lose weight because it revs up your metabolism’. But the thermic effect of food (or dietary induced thermogenesis) actually only accounts for 10 to 15 percent of total daily energy expenditure. So while you can try to eat more and different foods to rev up your metabolism, you are more likely to overeat than to notice a huge change in your rate of burning calories.”

“Daily energy expenditure consists of three components: basal metabolic rate, diet-induced thermogenesis [DIT] and the energy cost of physical activity. […] Diet induced thermogenesis is related to the stimulation of energy-requiring processes during the post-prandial period. […] The main determinant of DIT is the energy content of the food, followed by the protein fraction of the food. […] The main effect of protein on energy balance is thought to be DIT related satiety. […] The DIT increases body temperature, which may be translated into satiety feelings.” – Diet induced thermogenesis, a review


An example of a "non-scale victory" from Clark-Ganheart's Instagram.
An example of a “non-scale victory” from Clark-Ganheart’s Instagram.

Evolved to Fast and Non-Scale Victories

“The best of all medicines are resting and fasting.” – Benjamin Franklin

“We probably were never built for around-the-clock eating,” Clark-Ganheart says. She is right – from an evolutionary perspective, fasting makes sense. We evolved to handle periods of feast and famine, or intermittent fasting followed by periods of refeeding after a big hunt.

“We’ve gotten away from it in modern society, but hopefully we will get back to incorporating some kind of break from food consumption, whether that’s just going four hours between meals or practicing 12-hour overnight fasting, as a standard healthy lifestyle practice,” Clark-Ganheart said.

If fasting is baked into our evolutionary past and our genomic and metabolic present, it makes sense that fasting has health implications that go far beyond weight loss. Reduced oxidative stress and inflammation, increased efficiency of the cellular powerplants known as mitochondria, a more robust gut microbiome, greater insulin sensitivity and even improved brain function are just some of the “non-scale victories” to be had with a regular intermittent fasting practice.

Clark-Ganheart is personally passionate about raising the awareness of these “non-scale victories” through her health-related Instagram account. She encourages others to approach intermittent fasting in a way that is most sustainable for them, without too much of an emphasis, especially at first, on the scale.

“There are so many health factors and disease states that go beyond what you look like in the mirror,” Clark-Ganheart said. “It doesn’t matter if your BMI is 44 or 22 – there is probably still some benefit you could get from periodic fasting.”

The focus on the scale is also a problem that pervades the healthcare community. Many physicians, when they see a patient who looks lean and fit, may automatically assume the patient is healthy and doesn’t need advice about nutrition, increasing fruit and vegetable intake, or improving other lifestyle health factors such as physical activity.

This healthcare bias, in terms of who gets lifestyle health recommendations, referral to a dietitian, early-stage screenings for disease, etc. can be even more insidious when it is guided by not just the physical fitness appearance of the patient, but also by their gender and race, for example.

Whole and organic foods can be be expensive, but intermittent fasting is free. It can also help you save resources for healthier meals.
Whole and organic foods can be be expensive, but intermittent fasting is free. It can also help you save resources for healthier meals.

Health Disparities and Lifestyle Wins

One of the things that Clark-Ganheart loves most about intermittent fasting, both for herself and as a recommendation for her patients, is that it is free.

“Not all of us are able to have a personal chef, hire a personal trainer, or even purchase fresh produce and grass-fed beef on a regular basis,” Clark-Ganheart said. “I tell my patients, yes, I know it’s expensive to eat healthy. But if you are fasting, and say you used to eat out every morning for breakfast but now you are packing your meals for lunch, you actually can afford that organic spinach or grass-fed beef for your dinner meal.”

Lifestyle health interventions that are free and that could even save patients money are valuable at a time and in a country where there are large gaps in access to and equal treatment in healthcare based on gender, race and socioeconomic status.

“African American women are anywhere from 2 to 4 times more likely to die in childbirth compared to women of Caucasian descent, and this is even when you correct for education, income and other factors,” Clark-Ganheart said. “Some of this is due to healthcare bias – there are studies that show that pain or complaints from African American women during pregnancy tend to be downplayed more compared to other races.”

African American women and other minorities may also get fewer or less complete recommendations for lifestyle interventions like nutrition or for early-stage cancer screenings, for example. While healthcare researchers are increasingly unraveling these problems and diving into solutions for healthcare disparities, the gaps are too big to leave in the hands of the healthcare system alone. Clark-Ganheart proposes that one of the things patients can do for themselves, to partially overcome these inherent healthcare disparities, is to adopt lifestyle factors that can improve their health before they need help from a healthcare provider.

“Our healthcare system is flawed. In order to achieve the desired patient outcomes, we must encourage patients to adopt healthier lifestyles,” Clark-Ganheart said. “By using food as medicine, patients can be better positioned to help themselves live a better quality and longer life. We must become advocates for our own health, until the healthcare system can be changed for the betterment of all humankind,” she continued.

Learn more about eating healthy on a budget here, and check out healthy budget-friendly recipes here.

Learn more about intermittent fasting here and with the LIFE Fasting Tracker Learning Library.