Intermittent Fasting: Is It Really All That?

“Dr. Romm,  Help! I’m so frustrated!” Liv, 54, was at a frustrating impasse. She’d been elated because  after years of being unable to lose a pound – and too often gaining weight when she tried to lost it – she’d lost 8 pounds within 3 weeks on an elimination diet in my 28 Day Gut Reset. On top of that, her brain fog and joint pain were clearing up. But then things stalled. After 8 more weeks of cutting out gluten, sugar, dairy and more, she hadn’t lost another pound. “What can I do?” she asked during one of our live FB events. “There is something you can do,” I explained to Liv – it’s called intermittent fasting and it can work wonders!  “Let me tell you more…”

Intermittent Fasting – A New Old Practice

Food trends come and go as quickly as fashion trends. The 1980s brought big hair, neon-colored clothes, and the cabbage soup diet. Replace your regularly scheduled meals for bowls of cabbage soup and you’d be skinny and healthy. The 90s brought grunge and low-fat foods of every stripe. Americans gained weight and our cholesterol went up – not down. Point being – not all trends are in our best interest (though I must admit to still having a fondness for cool T-shirts, jeans, and combat boots).

Then there are the classics – those choices that are perennially smart, even if we forget about them for awhile until they make a comeback. Take high-waisted jeans – so much better on most of us than the super low-riders of the early 2000s.

Today I want to talk about a food ‘fad’ that’s the rage – but actually, isn’t a fad at all. In fact, it’s a classic that’s been taken out of the closet, shaken out, and given a whole new look. It’s called intermittent fasting.

Fasting remains an important part of cultural, spiritual and religious traditions around the world and has been for thousands of years. Intermittent fasting, the practice of giving your digestion a longer time to rest in a 24-hour cycle than you usually do, is actually the most natural possible rhythm for human digestion. Modern life in western countries allows us to eat from the moment we wake up until the moment we go to bed. Hearty breakfasts and midnight snacks are practically an American tradition. And food is always on the ready to grab.  If you’re a New Yorker, you can even “order in” anything at any time! Yet overeating is a major cause of disease, inflammation, and even sometimes just plain old discomfort! 

Our pre-electricity, pre-refrigeration, and pre-home delivery ancestors couldn’t just open the fridge at 7 am or 11 pm, grab some ingredients and pop them in the microwave or on the stove. Fires had to be built to cook food. That meant wood had to be gathered. Water had to be procured. And the food had to be prepared. From scratch. This took time, and leftovers weren’t the norm. So breakfast wasn’t a get-up-and-go kind of thing. The chores that allowed food to be eaten had to be done first. Similarly, the sun set and our ancestors went to bed long before late night TV even starts in our modern world. Wild carnivorous animals might have been on the prowl at around the time you’re first tuning into Trevor Noah. So yeah – no late night snacks or midnight meals. Too much work and bait for the wild creatures. No thanks. I think I’ll wait until morning…

The result? They tended to be naturally leaner, and didn't suffer from the chronic diseases that are now becoming ubiquitous. And they almost all enjoyed a natural period of fasting that extended roughly from about 7 pm or so until mid-morning. And that’s basically what intermittent fasting is.

The Benefits of Intermittent Fasting

Your digestive systems wasn't mean to be “on” all the time. We have a natural period when we are meant to rest and digest – allowing our parasympathetic nervous system to do its healing magic and our bodies to dump all of the metabolic waste we’ve accumulated throughout the day. When we let this happen, for about 12-14 hours each night, it’s been shown to reduce inflammation and we potentially experience numerous health benefits: increased insulin sensitivity, improved asthma-related symptoms, improved biomarkers for a host of chronic conditions (including diabetes, breast cancer, and cardiovascular disease), weight loss, improved cognitive function, and prevention and even reduction of degenerative disease processes in the brain. It allows the body to draw energy from fat cells, experience the benefits of very mild ketosis (not anywhere near the magnitude of a ketogenic diet but with many of the same benefits and it's healthier and safer!) and promotes the conversion of unhealthy white fat (white adipose tissue or WAT) into brown fat, its much healthier cousin. It is one of the only eating patterns, aside from the Mediterranean diet – which can be combined perfectly with this – that consistently correlates with greater longevity in the scientific literature. 

Intermittent fasting also isn’t about restricting specific foods though it's based only on a diet that consists of healthy, whole foods. It's about food timing – which done properly also naturally cuts calories by about 25% daily. Research has shown that by cutting calories this much for even just 5 days each month, we actually activate anti-aging/longevity promoting processes in our body, and increase not just the years in our life – but the life in our years!

While most of the scientific research has been done in animal studies, it is very promising for us – and again, it matches our most natural human rhythm for eating.  

The benefits of intermittent fasting come from the 12 (or more) hours when we don’t eat, but it can be more helpful to think about it from the positive perspective: it’s not a long stretch without food, it’s just a slightly shorter amount of time with food! You’re simply condensing your ‘eating hours’ into a slightly smaller window. So if you currently eat from 7:00 am until 9:00 pm, shrink the window a couple hours on either side. Try eating breakfast at 10:00 or 11:00 am and eating dinner no later than 7:00pm. Breakfast becomes “brunchfast” as I love to call it – and dinner becomes the “early bird” special. There’s generally no snacking in between, unless a bit of a light repast is needed to keep your energy up.

Many of my patients have adopted intermittent fasting practices that integrate easily into their busy lives and that don’t leave them feeling hungry day in and day out. In fact, a lot of my patients start intermittent fasting on a temporary basis, but they continue it indefinitely because they feel so good and because it’s really so easy. In addition to the above mentioned benefits, it can help with fatigue, joint inflammation, and weight loss resistance – and is even helpful if you feel healthy and want to stay that way. It’s one of the best ways to clean out the metabolic junk that builds up in the body over time. When we don’t give ourselves a rest from eating, health problems can arise and existing ones can get aggravated.



How to Practice Intermittent Fasting

An intermittent fast is a consecutive period of time without eating. Between the two meals you have each day, you can freely enjoy unsweetened, clear liquids – like water, herbal tea, and broth (bone or vegetable). 

Research suggests that the beneficial metabolic changes associated with fasting start at around 12 hours, though the benefits compound the longer you go. Sixteen hours seems to be the sweet spot for optimal benefits – but you can build up to that over time, or you can stay at 12 or 13 hours. Your body still benefits, and you will very likely notice big shifts in how you look and feel over time.  As you’ve likely noticed, your fasting window includes sleep time, making the fast significantly easier.

How you time the hours is up to you. If you give yourself an 8-hour window for eating and you prefer to eat from 10:00am to 6:00pm, that’s great. If you prefer to eat from noon until 8:00pm, that’s great, too. But it’s important to not go to sleep within 3-4 hours of eating your last meal of the day.

Is Intermittent Fasting for Everyone?

Like wearing a goose down coat in winter, sometimes it’s just not the right timing for you to try something on. If you are pregnant or breastfeeding, it's not an option – you need the nutrients from more meals – and this is not a time to be cutting back. Pregnant and nursing mommas need that more around the clock nutrition,

If you are currently or have recently struggled with an eating disorder, I don’t recommend intermittent fasting as it might be an unhealthy trigger for your mind and old patterns.

It’s also not always best – though not 100% contraindicated –  for women who are healing from fatigue due to low adrenal or thyroid function. While it can be helpful at reducing inflammation and improving brain fog and aches and pains, for some women skipping meals activates a primitive 4-alarm fire warning telling your body to conserve energy in case there’s a famine coming. The body then responds by further slowing down thyroid function and storing calories as fat. If you don’t have an adrenal or thyroid problem, it’s not an issue, and if you do and stay well nourished when you do eat, you might tolerate intermittent fasting as well – but tread carefully and listen to your body. If it’s not working for you, don’t keep doing it.

For me, as I've gotten older (I'm 51 now), it's a more natural daily eating pattern. However, it definitely doesn't work for me on especially demanding work days – for example, if I have to give a late morning presentation. I know to eat before any major work or physically strenuous events. It also might not be best for you if you do heavy workouts in the morning – in that case you can theoretically fast for the last meal of the day – but I find that this leads people to be hungry at night and not sleep as well, or even binge late at night so I don't recommend it. If you're a morning workout person, you can start your day with a protein shake, and then wait until closer to noon for your “breakfast” meal. Then don't have an afternoon snack of any kind and follow the rest of the plan for dinner, as described below.

What About Coffee?

A host of folks who talk about intermittent fasting on the internet will tell you how beneficial coffee, especially coffee ‘spiked’ with coconut oil, butter, and/or MCT oil is for intermittent fasting. (Some of those people also sell the products they're recommending.) But I don’t recommend it.  I’ve seen cholesterol go up rapidly with this practice and while coffee does have its health benefits, it can also spike your adrenaline and cortisol, and ultimately affect your blood sugar, adrenals, and thyroid, and make you feel hungry and agitated.

If at all possible, I recommend ditching the coffee at least on intermittent fasting days if you don't do it daily. If  you decide to intermittent fast daily, and you really love your coffee (I get it!) and just don’t want to go without it, have your one cup of the day (yes, one cup) of the regular kind of coffee (not all spiked up), organic, without all the extra coconut fat – just some organic milk or almond or coconut milk – with your ‘brunchfast' meal. That's now been shown to also be the optimal time of day to get the biggest bang for your coffee buck. 

The Art of the “Brunchfast” and the Rest of the Day…

How you break the fast is really important! Psychologically, you might be tempted to reward yourself with an all-you-can-eat meal. But this is counterproductive! You don’t want to consume the same amount of food you’d eat if you were grazing all day and evening in this shorter period of time. If you eat a giant feast your primitive brain will tell your body to store that extra energy in the form of fat for later use. Instead, I recommend breaking your fast with a simple, filling healthful meal containing:

  • Protein:  4 oz. of a clean animal protein, 2 eggs, or ½ cup of legumes or organic tofu or tempeh
  • Veggies: 2 cups of leafy greens (i.e., arugula, mixed greens, cooked kale, broccoli, spinach, etc.)
  • A healthy carb:  (a small sweet potato or baked potato cooled to room temp)
  • A serving of good quality fat: topped with olive oil and salt or 1/2 cup cooked grain (quinoa, brown rice, etc.)
  • A tablespoon or two of fermented veggies
  • A glass of water 

Then, between 1 and 3 PM, if you get hungry before your next meal, choose snacks that are high in healthy fat or protein, like nuts, bone broth, a hard boiled egg, or if you need something a little more, 8 oz. of a protein shake. If you want a sweet treat, have 1/2 cup organic fresh berries or 2 squares dark chocolate.

By 7 PM:

  • Have dinner which is the same composition as breakfast, just vary the foods + the water with apple cider vinegar.
  • No eating at all from 7 PM until 10 AM each day/evening.

Some people fast every day of the week. Some people fast 2-3 days each week.. You can try different rhythms and find what works for you.

What You Can Expect

While this is not for everyone, and it's important to pay attention to your body to discover how you feel eating this way, as Liv did, if you give it a try for at 4-6 weeks, you might find that your metabolism wakes up from hibernation and you shed some extra weight you’ve been carrying, your mental clarity and focus seem sharper, your energy more vibrant, your sleep becomes deeper and more refreshing – and you feel lighter, brighter, and younger. If you feel great, you can continue daily, several days each week, or you can intermittent fast – well – intermittently, for a little metabolic, mood, and brain boost now and then! 

Bronwen M. et al. Reduced energy intake: the secret to a long and healthy life? IBS J Sci. 2007 Sep; 2(2): 35–39.

Chaix, A. et al.. Time-Restricted Feeding Is a Preventative and Therapeutic Intervention against Diverse Nutritional Challenges. Cell Metabolism. 2014 Dec; 2(6):991–1005,

Harvie M and, Howell A. .Energy restriction and the prevention of breast cancer. Proc Nutr. Soc. 2012 May;71(2):263-75.

Kim, KH et al. Intermittent fasting promotes adipose thermogenesis and metabolic homeostasis via VEGF-mediated alternative activation of macrophage.Cell Research 2017 Volume 27:1309–1326

Mattson, MP & Wan, R. Beneficial effects of intermittent fasting and caloric restriction on the cardiovascular and cerebrovascular systems. J Nutr Biochem. 2005 Mar;16(3):129-37.

Michelle N. et al The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: a randomised trial in young overweight women. Int J Obes (Lond). 2011 May; 35(5): 714–727.

Weir, HJ. et al Dietary Restriction and AMPK Increase Lifespan via Mitochondrial Network and Peroxisome Remodeling. Cell Metabolism. 2017: Dec; 26(6):884–896.e5,

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I’m very interested in this but you have with dinner “water with AVC”. What is AVC? Did I miss this?

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    Tracy Romm

    So sorry, Mary. That was a typo - it should have been ACV for apple cider vinegar. We will make sure things are spelled out in the future rather than relying on abbreviations.

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Very informative and well written article!

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I have read lots on this, but this article was by far comprehensive and I could now understand! I have been following this for three days, and it has helped to break the cycle of eating whenever, although I eat “healthy.” Thank you Dr. Romm!

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    Tracy Romm

    We are so glad it helped, Cindy.

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Candace Tantarelli

Great article, thank you!!!

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Thanks Aviva, That was so informative and provides and easy-to-follow action plan. I'm going to start this evening. I strugle with intense brain fog and aching body, i have an underactive thyroid yet don't have weight issues, but do get heart palpitations and physical anxiety symptoms. I have just started reading your book Adrenal Thyroid Revolution. I don't have the money to see expensive specialists, or the energy to work more to get the money so it's feeling quite empowering to have a place to start. thank you so much. lucian

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Thank you Aviva. You really clarified intermittent fasting for me. You always break information down into easily digestible bites.

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Thank you Aviva. You really clarified intermittent fasting for me. Your posts ate always so infomative.