Intermittent fasting is safe for many people, but it's not for everyone. Skipping meals may not be the best way to manage your weight if you're pregnant or breast-feeding. If you have kidney stones, gastroesophageal reflux, diabetes or other medical problems, talk with your doctor before starting intermittent fasting.
Risks of Intermittent Fasting
You may become preoccupied with food, leading to overeating and weight gain. For example, when you don't eat for a long time, your body releases large amounts of the hormone ghrelin, which influences hunger. High ghrelin levels cause many to overeat during their eating windows.
As much as IF is filled with benefits, there are mild side effects that can happen during fasting, which do not generally require medical or surgical treatment. Possible side effects can include dizziness, nausea, insomnia, headache, weakness, etc.
Hundreds of animal studies and scores of human clinical trials have shown that intermittent fasting can lead to improvements in health conditions such as obesity, diabetes, cardiovascular disease, cancers and neurological disorders.
Both 12-hour fasting and 16-hour fasting can be effective for weight loss, but 16-hour fasting may be more effective because it may lead to a greater reduction in overall caloric intake (through a more condensed eating window) and promote more significant reliance on fat burning.
For example, studies have found that people who regularly fast more than 16 or 18 hours a day have a higher risk of gallstones. They're also more likely to need surgery to remove the gallbladder. Eating for 12 hours and then fasting for 12 hours is likely safe for most people, Longo explains.
The 4-4-12 method has a shorter fasting window—12 hours—but eliminates snacking between meals. The goal here is to fast for at least four hours between breakfast and lunch, four hours between lunch and dinner, and at least 12 hours between dinner and breakfast the next day.
If you don't eat for 10–16 hours, your body will go to its fat stores for energy, and fatty acids called ketones will be released into the bloodstream. This has been shown to protect memory and learning functionality, says Mattson, as well as slow disease processes in the brain.
Additionally, it will take your body a while to get used to this new eating schedule. So don't expect results right away. You may need to wait between 2 and 4 weeks to see or feel any results.
Avoid intermittent fasting if you have higher caloric needs.
Individuals who are underweight, struggling with weight gain, under 18 years of age, pregnant or breastfeeding should not attempt an intermittent fasting diet, as they need sufficient calories on a daily basis for proper development.
Suggested health benefits of intermittent fasting include healthy weight loss, a reduction in inflammation, a stronger immune system, a healthier heart, a more focused outlook, and even longer life.
With prolonged stress (including fasting), the hypothalamus will "turn down" the production of reproductive hormones that are important for ovulation and a healthy menstrual cycle. So it's possible for fasting to be "too much" of a stressor in some women, stressing them enough to prevent healthy ovulation.
Metabolic switching through intermittent fasting results in improved metabolism, increased health span, and increased longevity through multiple processes [16,30].
While drinking black coffee is fine during intermittent fasting, adding ingredients such as milk, cream, plant-based milk, sugar, or creamers can impact your metabolism and blood sugar. This, in turn, can disrupt the metabolic benefits you're striving for by fasting and negate the purpose of intermittent fasting.
Long story short - the answer to the question “Does lemon water break a fast?” is no, lemon water does not break a fast. Lemon water contains almost no calories and zero sugars, it doesn't raise insulin levels, which means it will not break your fast (1).
Splitting your day between 12 hours of eating and 12 hours of fasting has health benefits beyond just losing inches, including heart health and improved insulin sensitivity.
And yes, sleeping counts as fasting! If you are looking for significant weight loss, you might consider working up to 18-20 hours of daily fasting (OMAD or one-meal-a-day), alternate day fasting (fasting every other day, with up to 500 calories on fasting days) or a 5:2 schedule (fasting for two days per week).
Whole grains like quinoa and oats can be good to eat after fasting. Quinoa is a complete source of protein, rich in fiber, and naturally gluten-free. Oats and oatmeal can also be nourishing, filling, and not particularly hard to digest.
Julie Upton, MS, RD, and cofounder of Appetite for Health, said that most dietitians recommend a form of intermittent fasting that fits within someone's lifestyle, and a 14-hour fasting window is more doable than a 16-hour fasting window.
16/8 fasting is the most popular intermittent fasting method. It is a bit more advanced than the first two versions, but still very beginner-friendly. You eat within an eight-hour period every day and fast for 16 hours. Most people eat two meals during this period: Either breakfast and lunch or lunch and dinner.
You will generally experience more fat burning with a 16 vs 12 hour fast because the longer fasting duration allows you to burn through more of your glycogen stores. This is a crucial first step before significant fat burning and ketosis can set in.
If you are looking to experience more of the reported health benefits then the 20:4 might be a better option. If your only focus is weight loss, then again, the 20:4 fasting method is likely to be a better option.