Intermittent fasting, commonly referred to as IF, has become all the rage lately, and it doesn't look like the trend is going away anytime soon. The practice of intermittent fasting, or time-restricted feeding, is when a person limits the period of time in which they consume calories down to a limited number of hours. So for example, I practice IF with an eight-hour eating window, which means that I will only eat between the hours of 12 p.m. and 8 p.m.
None of the coffee additives caused a significant drop in our blood ketone levels. At 120 minutes, my, (Becky’s), ketone readings increased after drinking black coffee, coffee with cream, coffee with MCT oil, and coffee with butter. At 120 minutes, Keith’s ketone readings dropped by 0.1 mmol/L after drinking only black coffee. His ketone readings rose slightly after consuming coffee with cream, MCT oil, and butter.
Alternate between days where you eat normally, and days where you take in fewer than 600 calories. Some participants will even go so far as to eliminate food altogether during the off days. Just remember to stay hydrated while fasting, and be aware of what your body is telling you. If you find yourself feeling faint (instead of just hungry) then this may not be the best option for you.
For this plan, eat clean for five days of the week (you can pick whatever days you want). On the other two days, restrict your calories to no more than 700 each day. Calorie restriction unlocks a lot of the same benefits as fasting for an entire day. On your non-fasting days, you’ll need to make sure you're getting in healthy fats, clean meats, vegetables, and some fruits, and you can structure your meals however best works for you. On restricted days you can have smaller meals or snacks throughout the day or have a moderate-size lunch and dinner and fast in the morning and after dinner. Again, focus on healthy fats, clean meats, and produce. An app like MyFitnessPal can help you log your food and keep track of your calorie intake so you don’t go over 700.
Zero-calorie beverages are okay.  I drink green tea in the morning for my caffeine kick while writing. If you want to drink water, black coffee, or tea during your fasted period, that’s okay.  Remember, don’t overthink it – keep things simple! Dr. Rhonda Patrick over at FoundMyFitness believes that a fast should stop at the first consumption of anything other than water, so experiment yourself and see how your body responds.
I started IT about 6 weeks ago. I eat between 12 noon and 8 pm. This works best for me and I have found easily sustainable. The results so far have blown my mind. I have an autoimmune disease and struggled with bloating, multiple food intolerance, gut pain, frequent urination, sugar cravings. All of these symptoms are gone. My hunger is controlled and I can enjoy lovely family dinners again. I think ideally eating earlier in the day would be better, but due to my schedule this works better for me and I am happy with the results.
I am a 65-year-old male who started IF seven weeks ago. I only eat between noon and 8pm. I am obese, but losing about a pound a week so far. Notably, except for time, I have not changed what I eat at all. My diet was never terrible or great, and now it is the same, a mix of raw fruit sometimes and a donut another time. But I only eat it during the appointed hours. Remarkably, I do not feel hungry. I used to eat comfort breakfasts like pancakes or waffles, and I thought I would miss them. But no, I truly am not hungry in the mornings. I often delay lunch, but I still stop eating at 8. That alone probably has cut many calories of desserts. Bottom line: works for me so far.
IF as a weight loss approach has been around in various forms for ages, but was highly popularized in 2012 by BBC broadcast journalist Dr. Michael Mosley’s TV documentary Eat Fast, Live Longer and book The Fast Diet, followed by journalist Kate Harrison’s book The 5:2 Diet based on her own experience, and subsequently by Dr. Jason Fung’s 2016 bestseller The Obesity Code. IF generated a steady positive buzz as anecdotes of its effectiveness proliferated.
Does adding cream to your coffee make you hungrier throughout the rest of your fast? If yes, then you know you have spiked an insulin response and cream is a no-go for you! Hunger and cravings initially are common, but after a few days of routine fasting, if these symptoms continue, it is an indication that something is triggering an insulin response in you, causing these cravings. Is it something you’re adding to your coffee?
You’re consuming less food and thus spending less money. Rather than overeating to put on 1 pound of muscle and 4 pounds of fat in a week or two, you’re aiming to eat exactly enough to put on 1 pound of muscle without adding much fat on top of it.  Yeah, it’s a delicate balance, but there’s far less swing involved. You are just slowly, steadily, and consistently building muscle and strength over many months.
Those studies above, in working with small sample sizes, and different types of fasting than recommended here, would lead me to believe that fasting affects men and women differently, and that many of the weight loss benefits associated with intermittent fasting (that affect insulin and glucose responses) work positively for men and negatively for women.
As a lifestyle-leaning research doctor, I needed to understand the science. The Obesity Code seemed the most evidence-based summary resource, and I loved it. Fung successfully combines plenty of research, his clinical experience, and sensible nutrition advice, and also addresses the socioeconomic forces conspiring to make us fat. He is very clear that we should eat more fruits and veggies, fiber, healthy protein, and fats, and avoid sugar, refined grains, processed foods, and for God’s sake, stop snacking. Check, check, check, I agree. The only part that was still questionable in my mind was the intermittent fasting part.

It has totally regulated my appetite and normalised my relationship with food. My obsessive thoughts have completely subsided, my black and white thinking around food has gone, and I no longer binge! This is amazing. For the first time in my adult life I feel like I know what it is like to have a normal relatinoship with food. I eat when I eat, a range of healthy whole foods and occasional less healthy foods. In normal amounts. In manageable amounts. And when my meal is over, I stop! Normal for others, a seeming impossibility for me (and, I’m guessing, others with eating disorders).


I believe this is a disservice to those, like me, with a history of eating disorder. It has made experimenting with IF unnecessarily stressful. Despite my worry about what might happen (reading all these baseless cautions), I went ahead and experimented. In my experience, contrary to this “expert advice”, IF has been the most profoundly effective intervention I’ve experienced for my bulemia.
One potential disadvantage of this schedule is that because you typically cut out a meal or two out of your day, it becomes more difficult to get the same number of calories in during the week. Put simply, it's tough to teach yourself to eat bigger meals on a consistent basis. The result is that many people who try this style of intermittent fasting end up losing weight. That can be a good thing or a bad thing, depending on your goals.
You’ll run out of energy. When you don’t have anything in your system for several hours, your blood sugar will eventually drop below baseline. If you’ve ever had a blood sugar crash, you know how this state feels. Sleepiness, trouble focusing, lightheadedness, intense cravings, and the occasional mood swing typically accompany low blood sugar. Your cells run low on fuel and they start demanding that you give them more carbs.[13]
This process can be used as a way to get you into ketosis more quickly, so you can transition gracefully into a ketogenic lifestyle or as a way to stimulate autophagy and fat loss. If you can’t go without fat for the full 3 day fast — it’s okay — you will still illicit many of the benefits of fasting by limiting your protein and carbohydrate intake.

Low carb diets are designed to force your body to burn stored fat as its primary source of fuel. With a typical diet, carbohydrates are burned first, followed by protein, and then fat as the final source of fuel. However, because most people consume far more carbohydrates than are necessary, the excess calories are stored as fat and weight loss is difficult to achieve.

Make sure you still eat enough. Intermittent fasting does help you naturally eat less during the day, but be sure you’re still eating nutritious ketogenic foods to avoid any deficiencies or metabolic issues. Use a website or app to calculate ideal caloric intake and your ketogenic macros for each day, then track them to make sure you’re getting sufficient nutrition.

Fat loss. Keto and intermittent fasting are a one-two punch for losing weight. Fasting and keto both spontaneously increase fat loss, even when people don’t intentionally restrict their calories.[18][19] When you pair intermittent fasting and keto together, you become a fat-burning machine. The weight comes off quickly, and because keto also suppresses ghrelin, you don’t get nearly as much of the hunger and feelings of deprivation that usually accompany weight loss.
Surprisingly, since I've started intermittent fasting I've increased muscle mass (up 10 pounds from 205 to 215), decreased body fat (down 3% from 14% to 11%), increased explosiveness (set a personal best with a clean and jerk of 253 pounds a few months back), and decreased the amount of time I've spent training (down from 7.5 hours per week to 2.5 hours per week).
There are MUCH bigger fish to fry with regards to getting healthy than a few calories here and there during a fast. 80% adherence that you stick with for a year is better than 100% adherence that you abandon after a month because it was too restrictive. If you’re trying to get to a minimum bodyfat percentage, you’ll need to be more strict – until then, however, do what allows you to stay compliant!
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