So what if you think you could restrict your eating to fewer than eight hours, but aren’t sure you could commit to alternate-day fasting? You might want to try shortening your daily eating window a little bit more. Varady and her team are currently in the process of comparing 4-hour and 6-hour eating windows for shedding pounds. “We are curious to see if these shorter eating windows result in more rapid weight loss compared to 8-hour time restricted feeding,” she says.
Intermittent fasting (intermittent energy restriction or intermittent calorie restriction) is an umbrella term for various eating diet plans that cycle between a period of fasting and non-fasting over a defined period. Intermittent fasting is under preliminary research to assess if it can produce weight loss comparable to long-term calorie restriction.[1][2][3][4][5]

In many developing countries, the ketogenic diet is expensive because dairy fats and meat are more expensive than grain, fruit and vegetables. The modified Atkins diet has been proposed as a lower-cost alternative for those countries; the slightly more expensive food bill can be offset by a reduction in pharmaceutical costs if the diet is successful. The modified Atkins diet is less complex to explain and prepare and requires less support from a dietitian.[55]
That said, I have heard that women may find a wider window of eating to be more favorable when doing daily intermittent fasting. While men will typically fast for 16 hours and then eat for 8 hours, women may find better results by eating for 10 hours and fasting for 14 hours. The best advice I can give anyone, not just women, is to experiment and see what works best for you. Your body will give you signals. Follow what your body responds favorably to.
The ketone bodies are possibly anticonvulsant; in animal models, acetoacetate and acetone protect against seizures. The ketogenic diet results in adaptive changes to brain energy metabolism that increase the energy reserves; ketone bodies are a more efficient fuel than glucose, and the number of mitochondria is increased. This may help the neurons to remain stable in the face of increased energy demand during a seizure, and may confer a neuroprotective effect.[56]
The ketone bodies are possibly anticonvulsant; in animal models, acetoacetate and acetone protect against seizures. The ketogenic diet results in adaptive changes to brain energy metabolism that increase the energy reserves; ketone bodies are a more efficient fuel than glucose, and the number of mitochondria is increased. This may help the neurons to remain stable in the face of increased energy demand during a seizure, and may confer a neuroprotective effect.[56]
On a ketogenic diet, your entire body switches its fuel supply to run mostly on fat, burning fat 24-7. When insulin levels become very low, fat burning can increase dramatically. It becomes easier to access your fat stores to burn them off. This is great if you’re trying to lose weight, but there are also other less obvious benefits, such as less hunger and a steady supply of energy. This may help keep you alert and focused.
In terms of weight loss, you may be interested in trying the ketogenic diet because you’ve heard that it can make a big impact right away. And that’s true. “Ketogenic diets will cause you to lose weight within the first week,” says Mattinson. She explains that your body will first use up all of its glycogen stores (the storage form of carbohydrate). With depleted glycogen, you’ll drop water weight. While it can be motivating to see the number on the scale go down (often dramatically), do keep in mind that most of this is water loss initially.
There are three instances where there’s research to back up a ketogenic diet, including to help control type 2 diabetes, as part of epilepsy treatment, or for weight loss, says Mattinson. “In terms of diabetes, there is some promising research showing that the ketogenic diet may improve glycemic control. It may cause a reduction in A1C — a key test for diabetes that measures a person’s average blood sugar control over two to three months — something that may help you reduce medication use,” she says.
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.
In terms of weight loss, you may be interested in trying the ketogenic diet because you’ve heard that it can make a big impact right away. And that’s true. “Ketogenic diets will cause you to lose weight within the first week,” says Mattinson. She explains that your body will first use up all of its glycogen stores (the storage form of carbohydrate). With depleted glycogen, you’ll drop water weight. While it can be motivating to see the number on the scale go down (often dramatically), do keep in mind that most of this is water loss initially.
^ Jump up to: a b c d e f g h i j k l m n o p q r s Kossoff EH, Zupec-Kania BA, Amark PE, Ballaban-Gil KR, Bergqvist AG, Blackford R, et al. Optimal clinical management of children receiving the ketogenic diet: recommendations of the International Ketogenic Diet Study Group. Epilepsia. 2009 Feb;50(2):304–17. doi:10.1111/j.1528-1167.2008.01765.x. PMID 18823325
I'd love to say I lost 10 pounds in a week, but my body doesn't really work that way. And besides, I only fasted 7 days. I'm definitely eating less food and weirdly feeling less hungry, which over time will result in fat loss. But we all know that if you're only following an eating plan because of weight loss, you're bound to fail. That's because, when the scale gets stuck, and it will, we're quick to throw in the towel. It's intermittent fasting's built-in intrinsic motivation that keeps me going. My energy, focus, and motivation have all skyrocketed, and I've learned how to tell my hunger pangs who's boss. Love handles, you're next!

When you eat less than 50 grams of carbs a day, your body eventually runs out of fuel (blood sugar) it can use quickly. This typically takes 3 to 4 days. Then you’ll start to break down protein and fat for energy, which can make you lose weight. This is called ketosis. It's important to note that the ketogenic diet is a short term diet that's focussed on weight loss rather than the pursuit of health benefits. 
Insulin is a hormone that lets your body use or store sugar as fuel. Ketogenic diets make you burn through this fuel quickly, so you don’t need to store it. This means your body needs -- and makes -- less insulin. Those lower levels may help protect you against some kinds of cancer or even slow the growth of cancer cells. More research is needed on this, though.
While the 16:8 diet seems like a great way to drop weight fast, it does have some cons. Sarah Mirkin, RD, author of Fill Your Plate, Lose the Weight, a 21-day meal plan designed to help women over 40 lose weight, says, "I think that it limits food intake to such a small window of time that it's difficult for someone to meet their nutritional needs."
The best diet is one that you can stick with, and that means finding a plan that fits into your daily routine. If you already tend to eat dinner on the early side, the 16:8 diet could be great. But for some people, stopping eating by 6 p.m. could have a negative impact on their social lives—dinner or drinks with friends could get trickier. (Still, there's always weekend brunch!) It might impact things at home too, if your family tends to eat on the later side. “People should choose the diet that best fits with their lifestyle and weight loss goals,” Varady says.

A Cochrane systematic review in 2018 found and analysed eleven randomized controlled trials of ketogenic diet in people with epilepsy for whom drugs failed to control their seizures.[2] Six of the trials compared a group assigned to a ketogenic diet with a group not assigned to one. The other trials compared types of diets or ways of introducing them to make them more tolerable.[2] In the largest trial of the ketogenic diet with a non-diet control[16], nearly 38% of the children and young people had half or fewer seizures with the diet compared 6% with the group not assigned to the diet. Two large trials of the Modified Atkins Diet compared to a non-diet control had similar results, with over 50% of children having half or fewer seizures with the diet compared to around 10% in the control group.[2]
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.
There are theoretically no restrictions on where the ketogenic diet might be used, and it can cost less than modern anticonvulsants. However, fasting and dietary changes are affected by religious and cultural issues. A culture where food is often prepared by grandparents or hired help means more people must be educated about the diet. When families dine together, sharing the same meal, it can be difficult to separate the child's meal. In many countries, food labelling is not mandatory so calculating the proportions of fat, protein and carbohydrate is difficult. In some countries, it may be hard to find sugar-free forms of medicines and supplements, to purchase an accurate electronic scale, or to afford MCT oils.[54]

If you think you may have a medical emergency, call your healthcare provider or 911 immediately. Any mention of products or services is not meant as a guarantee, endorsement, or recommendation of the products, services, or companies. Reliance on any information provided is solely at your own risk. Please discuss any options with your healthcare provider.
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.

During the 1920s and 1930s, when the only anticonvulsant drugs were the sedative bromides (discovered 1857) and phenobarbital (1912), the ketogenic diet was widely used and studied. This changed in 1938 when H. Houston Merritt, Jr. and Tracy Putnam discovered phenytoin (Dilantin), and the focus of research shifted to discovering new drugs. With the introduction of sodium valproate in the 1970s, drugs were available to neurologists that were effective across a broad range of epileptic syndromes and seizure types. The use of the ketogenic diet, by this time restricted to difficult cases such as Lennox–Gastaut syndrome, declined further.[10]
It’s natural for anyone trying to lose weight to want to lose it very quickly. But evidence shows that people who lose weight gradually and steadily (about 1 to 2 pounds per week) are more successful at keeping weight off. Healthy weight loss isn’t just about a “diet” or “program”. It’s about an ongoing lifestyle that includes long-term changes in daily eating and exercise habits.
After that timespan, your body goes into what is known as the post–absorptive state, which is just a fancy way of saying that your body isn’t processing a meal. The post–absorptive state lasts until 8 to 12 hours after your last meal, which is when you enter the fasted state. It is much easier for you body to burn fat in the fasted state because your insulin levels are low.

I would like to know what led you to the conclusion to recommend eating in the morning and fasting in the evening instead of the other way around. You do not link any studies here that show TRF in the morning is better than TRF in the evening. You do state “Nighttime eating is well associated with a higher risk of obesity, as well as diabetes.” but I would hazard a guess that alot people that snack into the evening have many other factors at play that could effect their risk of obesity and diabetes and are possibly not fasting at all. I have been doing TRF from 12-8pm every day for almost a year and have seen vast improvements in my health, not least of which is a loss of 70 lbs, so it seems odd to read items 3 and 4 on your 4 ways to use this information for better health. If you have evidence that supports the idea that TRF in the evening is bad then I would like to see it and perhaps change my dieting habbits.
Not around your waist, but on your plate: A new report from the Credit Suisse Research Institute found that more and more of us are choosing whole-fat foods over skim, lite, fat-free or other modern monikers of leanness. And while many health organizations like the American Heart Association still want us to cut down on fat—particularly saturated fat—this full-fat trend may be a healthy rebellion against those decades-old credos, according to recent studies. Click here to discover The 20 Best Full-Fat Foods for Weight Loss!
Advocates for the diet recommend that it be seriously considered after two medications have failed, as the chance of other drugs succeeding is only 10%.[9][31][32] The diet can be considered earlier for some epilepsy and genetic syndromes where it has shown particular usefulness. These include Dravet syndrome, infantile spasms, myoclonic-astatic epilepsy, and tuberous sclerosis complex.[9][33]
Forms of intermittent fasting exist in religious practices in various groups across the world.[11] Religious fasting regimens include, but are not limited to, Vrata in Hinduism, Ramadan fasting (Islam), Yom Kippur fasting (Judaism), Orthodox Christian fasting, Fast Sunday (The Church of Jesus Christ of Latter-day Saints), and Buddhist fasting.[11] Certain religious fasting practices, only require abstinence from certain foods, while others, like the Jewish fast on Yom Kippur, last for a short period of time and would cause negligible effects on the body.[11]
The ketogenic diet is indicated as an adjunctive (additional) treatment in children and young people with drug-resistant epilepsy.[26][27] It is approved by national clinical guidelines in Scotland,[27] England, and Wales[26] and reimbursed by nearly all US insurance companies.[28] Children with a focal lesion (a single point of brain abnormality causing the epilepsy) who would make suitable candidates for surgery are more likely to become seizure-free with surgery than with the ketogenic diet.[9][29] About a third of epilepsy centres that offer the ketogenic diet also offer a dietary therapy to adults. Some clinicians consider the two less restrictive dietary variants—the low glycaemic index treatment and the modified Atkins diet—to be more appropriate for adolescents and adults.[9] A liquid form of the ketogenic diet is particularly easy to prepare for, and well tolerated by, infants on formula and children who are tube-fed.[5][30]

Hi Thea, That’s wonderful that IF has worked for you. Diets, and particularly fasting, can be very triggering for others with a history of an eating disorder. People who have been in remission can relapse. For more about what concerns and problems others have had, there is alot of information out there, and for starters I recommend this thorough article from Psychology Today: https://www.psychologytoday.com/us/blog/hunger-artist/201411/the-fast-diet-fast-route-disordered-eating
Another program called the 5:2 Fast Diet involves eating 5 days a week and fasting for the other 2 days, when women can get no more than 500 calories and men no more than 600. That’s a quarter of the amount you likely eat on the days when you don’t fast. Whether you eat those calories in one sitting or spread them across micro-meals throughout the day is up to you.
Con: Results can vary depending on how much fluid you drink. By drinking more water, you dilute the concentration of ketones in the urine and thus a lower level of ketones will be detected on the strips. The strips don’t show a precise ketone level. Finally, and most importantly, as you become increasingly keto-adapted and your body reabsorbs ketones from the urine, urine strips may become unreliable, even if you’re in ketosis.
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