This is excellent, thank you! One thing I would love to see added to this research is the keto effect of just water over those 120 minutes, and THEN the keto effect of adding a tad bit of protein, such as collagen powder (I use the green tub great lakes powder; it dissolves great in coffee). I feel like that might put your test even more into an annals of science, and for us folks who don’t have the finger prick blood testers, it would be fun to know. Also, sugar free sweeteners like splenda (!!) or stevia–do they have any effect? Anyway–great read, exactly what I was looking for when I googled my question.
So here’s the deal. There is some good scientific evidence suggesting that circadian rhythm fasting, when combined with a healthy diet and lifestyle, can be a particularly effective approach to weight loss, especially for people at risk for diabetes. (However, people with advanced diabetes or who are on medications for diabetes, people with a history of eating disorders like anorexia and bulimia, and pregnant or breastfeeding women should not attempt intermittent fasting unless under the close supervision of a physician who can monitor them.)
A 2018 review of intermittent fasting in obese people showed that reducing calorie intake one to six days per week over at least 12 weeks was effective for reducing body weight on an average of 7 kilograms (15 lb); the results were not different from a simple calorie restricted diet, and the clinical trials reviewed were run mostly on middle-aged women from the US and the UK, limiting interpretation of the results. Intermittent fasting has not been studied in children, the elderly, or underweight people, and could be harmful in these populations.
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.
Crescendo fasting only requires you to fast a few days a week instead of every day. My experience is that women get a lot more benefit from doing it this way without accidentally throwing their hormones into frenzy. This is a more gentle approach that helps the body more easily adapt to fasting. And if women do it right, it can be an amazing way to shave off body fat, improve inflammatory markers and gain energy. (7)
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.
While it’s not technically fasting, some doctors have reported intermittent fasting benefits by allowing such easy-to-digest food as whole fruit during the fasting window. Modifications like these can still give your digestive and metabolic system a needed rest. For example, “Fit for Life” was a popular weight loss book that suggested eating only fruit after supper and before lunch.
There are different types of intermittent fasting, but the most common involves only eating within a certain window of time each day. For example, you might only eat between 12pm and 6pm each day, giving you a 6-hour “feeding” window when you eat all of your calories for the day. That means you’ll be fasting for 18 hours in between. Your intermittent fasting ratio would then be 18/6.
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You drink sugary beverages, digest them quickly and store the leftovers as body fat. After the initial spike in blood sugar, you experience a dramatic drop, which prompts you to eat more, and what happens? You store more fat. Because of this, it's best to avoid sugary drinks, like soda, lemonade, fruit juices, sweetened iced tea and even some kombucha, completely, whether you're fasting or not.
I’ll share some of my experiences, now doing heavy strength training for 3 years in a fasted state: For my first “fasted” workout or two after starting an IF protocol, it was very weird to not eat before training. However, after a few sessions, I learned that my body could certainly function (and even thrive) during my training sessions despite not eating a pre-workout meal.