Intermittent fasting (IF) side effects often include initial hunger, headaches, fatigue, irritability, low energy, and sleep issues, as the body adjusts. Digestive problems (like constipation), dehydration, and mood swings can also occur. While generally mild and temporary, severe or long-term risks can involve malnutrition, disrupted hormones, and potentially triggering eating disorders, so consulting a doctor is key, especially for those with underlying conditions or women.
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.
There are numerous health risks associated with intermittent fasting. Research reveals a range of negative physical and mental side effects of intermittent fasting. Like most restrictive diets, side effects include—but are not limited to—hunger, headaches, fatigue, and mood disturbances.
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.
Yes it is possible in order to lose 5 kg in two weeks, you would need to create a calorie deficit of approximately 35000 calories.
Best Fasting-Friendly Drinks
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.
For example, a news release published last year after an American Heart Association meeting reported some potentially concerning findings — namely, that people who followed an 8-hour, time-restricted eating schedule, a type of intermittent fasting, had a 91% higher risk of dying from heart disease.
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.
Following an intermittent fasting skip dinner approach might be better aligned with your circadian rhythm. This way, you can improve digestion and sleep by preventing late-night overeating. Beginning your intermittent fasting with breakfast early in the morning can also help reduce your overall calorie intake.
Regardless of the intermittent fasting form people choose, they tend to make the same five common mistakes:
22:2 fasting, also known as the OMAD (One Meal A Day) diet, is a form of intermittent fasting where you fast for 22 hours and eat all your daily calories within a compact 2-hour window, focusing on nutrient-dense foods to support weight loss, improve digestion, and boost mental clarity, though research on its long-term safety and effectiveness is limited. It's an intense, restrictive schedule that helps reduce overall calorie intake and may trigger autophagy (cellular cleanup), but requires careful attention to nutrition during the eating window to avoid deficiencies.
Quick answers for managing hunger while fasting:
Eat a higher-protein, low-carb breakfast instead, like meat and nuts, an omelet, or a low-carb protein shake. Just don't knock the intermittent fasting unless you've really tried it.
Weight Loss
If you adopt a 16:8 intermittent-fasting approach to your nutrition, you are likely to spontaneously reduce your energy intake by approximately 20–30% or 350–500 calories. Within a month of consistent 16:8 intermittent fasting, you can expect to lose 2–5% of your body weight.
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.
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.
Signs You're Benefiting From Intermittent Fasting
Anyone under 18, those who are pregnant or breastfeeding, and individuals who have had disordered eating should avoid intermittent fasting. If you have certain medical conditions or take certain medications, intermittent fasting may impact them, so it's important to discuss it with your doctor.
Ideally, the association of fasting and lower blood pressure levels means a possible decrease in hypertension-related complications due to the reduction of the workload on the heart. However, the evidence supporting the direct impact of fasting on cleaner arteries is not conclusive.
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.
People naturally lose muscle after 40, especially women after menopause. Because muscle burns more calories than fat, this can slow down your metabolism and make it harder to shake those stubborn pounds.