Most people make an IF schedule that requires them to fast for 12 to 16 hours a day. During the rest of the time, they eat normal meals and snacks. Sticking to this eating window isn’t as hard at it sounds because most people sleep for about eight of their fasting hours. In addition you’re encouraged to enjoy zero-calorie drinks, like water, tea, and coffee.


Some people believe that IF has worked for them simply because the limited eating window naturally helps them reduce the amount of calories they consume. For instance, instead of eating three meals and two snacks, they might find that they only have time for two meals and one snack. They become more mindful about the kinds of food they consume and tend to stay way from processed carbs, unhealthy fat, and empty calories.
Cons: Even though there is flexibility in when you eat, Leangains has pretty specific guidelines for what to eat, especially in relation to when you’re working out. The strict nutrition plan and scheduling meals perfectly around workouts can make the program a bit tougher to adhere to. (You can learn more about the specifics — as well as when to time these meals — directly from Leangains here and here.)

That window can be shrunk or expanded depending on your needs and preferences but typically, it’s somewhere between 4-7 hours of feeding during the day. Intermittent fasting is a great practice for weight loss, appetite control, digestion, and health on its own. When it’s combined with the keto diet and its benefits, the results can be even better.
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.
Cons: Going 24 hours without any calories may be too difficult for some — especially at first. Many people struggle with going extended periods of time with no food, citing annoying symptoms including headaches, fatigue, or feeling cranky or anxious (though these side effects can dimish over time). The long fasting period can also make it more tempting to binge after a fast. This can be easily fixed… but it takes a lot of self-control, which some people lack.

Cons: Even though there is flexibility in when you eat, Leangains has pretty specific guidelines for what to eat, especially in relation to when you’re working out. The strict nutrition plan and scheduling meals perfectly around workouts can make the program a bit tougher to adhere to. (You can learn more about the specifics — as well as when to time these meals — directly from Leangains here and here.)


On this plan you'll eat clean five days of the week but will not eat anything for two nonconsecutive days of the week. For example, you can fast on Monday and Thursday but eat clean meals on the other days. Food on these five days will look just like the rest of the fasting plans—healthy fats, clean meat sources, vegetables, and some fruit. Keep in mind that this plan is not for beginners, and you should always talk to your doctor before starting any fasting regimen, especially if you are on medication or have a medical condition.
So how long does it take to go into ketosis when fasting? On a standard keto diet, it typically takes around 2–3 days to reach ketosis, although it can take up to seven days in some cases. However, many people find that keto adaptation intermittent fasting can speed up the process and help your body burn through glycogen stores more quickly to help enter ketosis.
Conversely, a 2013 study completed by researchers at Washington University School of Medicine, presented the exact opposite, showing increased reactions in receptors on the tongue, when participants were given artificial sweeteners. Their study concluded that if the receptors are capable of detecting sweetness, even though calories aren’t present, a hormonal response (insulin release) is likely.

This content is strictly the opinion of Dr. Josh Axe and is for informational and educational purposes only. It is not intended to provide medical advice or to take the place of medical advice or treatment from a personal physician. All readers/viewers of this content are advised to consult their doctors or qualified health professionals regarding specific health questions. Neither Dr. Axe nor the publisher of this content takes responsibility for possible health consequences of any person or persons reading or following the information in this educational content. All viewers of this content, especially those taking prescription or over-the-counter medications, should consult their physicians before beginning any nutrition, supplement or lifestyle program.


Understanding the potential adverse effects of intermittent fasting is limited by an inadequate number of rigorous clinical trials. One 2015 review of preliminary clinical studies found that short-term intermittent fasting may produce minor adverse effects, such as continuous feelings of weakness and hunger, headaches, fainting, or dehydration.[29] Long-term, periodic fasting may cause eating disorders or malnutrition, with increased susceptibility to infectious diseases.[29]
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).
Many people achieve the best results by starting the ketogenic diet first and then beginning intermittent fasting several weeks later. Although this is a bit different from the classic approach to the keto-intermittent fasting diet, it works better for some individuals. This is because intermittent fasting, as previously mentioned, should be a natural process, during which you should not feel deprived and hungry.
For this reason, certain experts believe that intermittent fasting improves a broad range of neuro-degenerative conditions, including stroke, Huntington’s disease, Parkinson’s disease, and Alzheimer’s disease. After conducting a study on animals, researchers at the National Institute on Aging, found that cyclical fasting helps neurons in the brain to resist degeneration and dysfunction.
I dont think this test presents the whole picture. Dairy products can spike insulin levels based on the protiens (not the carbs) in dairy products, without raising blood glucose. When intermittent fasting, part of the benefit is to take insulin out of the picture during the fast. You could be increasing yur insulin levels using dairy products but not see a change in blood glucose.
The four-hour eating window — which Hofmekler refers to as the “overeating” phase — is at night in order to maximize the Parasympathetic Nervous System’s ability to help the body recuperate, promoting calm, relaxation and digestion, while also allowing the body to use the nutrients consumed for repair and growth. Eating at night may also help the body produce hormones and burn fat during the day, according to Hofmekler. During these four hours, the order in which you eat specific food groups matters, too. Hofmelker says to start with veggies, protein and fat. After finishing those groups, only if you are still hungry should you tack on some carbohydrates.
Listen to your body during workouts. If you get light headed, make sure you are consuming enough water. If you notice a significant drop in performance, make sure you are eating enough calories (especially fats and protein) during your feasting window. And if you feel severely “off,” pause your workout. Give yourself permission to EASE into intermittent fasting and fasted workouts. This is especially true if you are an endurance athlete.
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