Fasting, particularly intermittent fasting, shows potential health benefits like weight loss, better blood sugar control, improved heart health (blood pressure, cholesterol), reduced inflammation, and enhanced brain function, but it also has risks like tiredness and irritability, and long-term effects aren't fully known; it's crucial to consult a healthcare professional before starting, as some people should avoid it. Benefits may stem from weight loss or the fasting process itself (like cellular repair through autophagy), with benefits often seen alongside overall calorie reduction.
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.
Longer periods without food, such as 24-, 36-, 48- and 72-hour fasting periods, are not necessarily better for you, and may be dangerous. Going too long without eating might actually encourage your body to start storing more fat in response to starvation.
Doctors are cautious about intermittent fasting (IF) due to potential risks like increased cardiovascular death (especially with <8hr windows), hormonal issues for women, muscle/bone loss, side effects (fatigue, headaches), risks for specific groups (diabetics, pregnant/elderly), and the lack of long-term data, with some studies showing similar benefits to general calorie restriction or suggesting risks that outweigh benefits, urging personalized medical advice.
“In the fasted state, the ability of cells to use lipids and fatty acids as an energy source enables them to survive when nutrients are low. And then it's the postfast refeeding state that really drives the regeneration.
The absolute most important rule is “don't break your fast." It's more important than how many calories you eat each day, or how you structure your meal timing. The core principle needed to take advantage of intermittent fasting is consecutive non-eating hours.
⚠️ CRITICAL SAFETY NOTICE: A 3-day water fast is a medical intervention that can affect blood sugar, blood pressure, and electrolyte balance. Always consult a healthcare provider before attempting any extended fast, especially if you have medical conditions, take medications, or have a history of eating disorders.
As blood glucose levels fall during fasting, the pancreas secretes increased amounts of glucagon. This action also reduces insulin secretion, which in turn decreases glucose storage in the form of glycogen.
The 3-3-3 rule for weight loss is a simple, habit-based method focusing on three key areas: 3 balanced meals a day, 3 bottles (or ~1.5L) of water by 3 PM, and 3 hours of physical activity per week, aiming for consistency over complex diets. It simplifies fat loss by establishing rhythm through consistent eating, adequate hydration to support metabolism, and regular movement, promoting sustainable health without intense calorie counting or restrictive rules, says Five Diamond Fitness and Wellness, Joon Medical Wellness & Aesthetics, and EatingWell.
Pregnant or breastfeeding people have increased energy needs and shouldn't engage in calorie restriction. 5 Intermittent fasting may also reduce your chances of becoming pregnant and should be avoided if you're trying to conceive. 6. You have diabetes or blood sugar issues.
During a 72 hour fast, you do not consume any food, nor any drinks with any calories. This extended fast offers several scientifically observed benefits, including increased autophagy (cellular cleanup), improved insulin sensitivity, reduced inflammation, weight loss, and potentially enhanced immune function.
Eating one meal a day can increase your blood pressure and cholesterol. This occurred in a group of healthy adults who switched to one meal a day to participate in a study. If you already have concerns in either area, eating just once a day might not be safe. Eating one meal late can cause your blood sugar to spike.
Yes, fasting from 7 p.m. to 7 a.m. (a 12-hour fast) is generally considered a good, easy-to-start form of intermittent fasting, promoting benefits like weight management, better blood sugar, improved gut health, and reduced inflammation by giving your body a consistent break to switch to burning fat for fuel, especially when paired with quality foods during the eating window. It's a sustainable, natural routine for many, but it's crucial to stay hydrated, eat whole foods, and consult a doctor if you have health conditions like diabetes.
He shares six tips for maintaining your health and energy level during a fast in which you don't eat at all.
Studies have shown that fasting as a dietary intervention substantially modifies the intestinal flora. Research has shown that it can decrease inflammation, increase bacteria diversity, and increase the synthesis of crucial microbial compounds, including SCFAs (Liu et al., 2020, Zhang et al., 2020).
Adele's significant weight loss wasn't from a quick fix but a two-year journey combining intense strength training, Pilates, hiking, boxing, and cardio, alongside major lifestyle changes focused on managing anxiety, not restrictive diets like the Sirtfood Diet, with workouts happening multiple times daily for mental and physical strength. Her routine included morning weights, afternoon hikes or boxing, and evening cardio, emphasizing getting stronger, which naturally led to fat loss and improved well-being.
Daily: The most common form of intermittent fasting is a daily fast for 12 to 16 hours. For a 16-hour fast, this would result in an 8-hour feeding window during a 24-hour period. A “16:8” fast might look like eating breakfast at 11am and finishing dinner by 7pm.
According to fitness coach Raj Ganpath, losing 10 kg in 2-3 months is possible but highly unsustainable. He explains that to achieve this, you need a daily calorie deficit of about 1,300, which is extremely difficult to maintain.
By giving the liver a break from constant digestion, fasting allows it to focus on repairing itself and reducing inflammation. Bile is essential for breaking down fats and removing waste from the liver. Fasting has been shown to improve the liver's ability to produce bile, which can further enhance detoxification.
Signs You're Benefiting From Intermittent Fasting
Stool production is significantly reduced during long-term fasting.
Higher LDL cholesterol and higher blood sugar levels in diabetes are risk factors for heart disease. But a recent study suggested that restricting eating times to fewer than eight hours a day may be linked to a higher risk of dying of heart disease.
In addition to losing weight, 24-hour fasting also has a positive effect on your body's metabolism, improving cardiovascular health, and more. You should use this method 1-2 times a week to ensure safety for your health. This method may seem easier than cutting down on daily calorie intake.
Many medical experts agree that a one-day fast can feel great. But extending beyond three days can begin to cause harm, especially if you have other medical conditions, such as diabetes or heart disease. “A fast longer than a day or two can deplete vitamins, minerals and electrolytes,” Dr. Hopkins says.