IF as a weight loss approach has been around in various forms for ages, but was highly popularized in 2012 by BBC broadcast journalist Dr. Michael Mosley’s TV documentary Eat Fast, Live Longer and book The Fast Diet, followed by journalist Kate Harrison’s book The 5:2 Diet based on her own experience, and subsequently by Dr. Jason Fung’s 2016 bestseller The Obesity Code. IF generated a steady positive buzz as anecdotes of its effectiveness proliferated.
The trick here is not only to avoid all obvious sources of carbohydrate (sweets, bread, spaghetti, rice, potatoes), but also to be careful with your protein intake. If you eat large amounts of meat, eggs and the like, the excess protein will be converted into glucose in your body. Large amounts of protein can also raise your insulin levels somewhat. This compromises optimal ketosis.
Nutrient-dense, good food is certainly the foundation of weight loss. But an adequate amount of vitamin D can be difficult to ingest via food, especially for those who are vegetarian or don’t eat fatty fish (the main dietary source of vitamin D) on a regular basis. In the case of a lack of sun (such as during the darker months of fall and winter), it’s wise to supplement for multiple health reasons – and perhaps even for your weight.
AN IMPORTANT CAVEAT: Intermittent Fasting can be more complex for people who have issues with blood sugar regulation, suffer from hypoglycemia, have diabetes, etc. If you fit into this category, check with your doctor or dietitian before adjusting your eating schedule. It also affects women differently (there’s a whole section dedicated to that here).
Those studies above, in working with small sample sizes, and different types of fasting than recommended here, would lead me to believe that fasting affects men and women differently, and that many of the weight loss benefits associated with intermittent fasting (that affect insulin and glucose responses) work positively for men and negatively for women.
Make sure that you don't get hungry by eating small portions throughout the day at regular intervals. Between your meals, eat a 150-calorie snack to keep your metabolism burning and to stave off hunger. Be sure that you don't eat a fattening snack such as sweets or crisps. When you're hungry, your body conserves calories and slows down your metabolic processes.
It seems strange that a diet that calls for more fat can raise “good” cholesterol and lower “bad” cholesterol, but ketogenic diets are linked to just that. It may be because the lower levels of insulin that result from these diets can stop your body from making more cholesterol. That means you’re less likely to have high blood pressure, hardened arteries, heart failure, and other heart conditions. It's unclear, however; how long these effects last.
If you want to lose weight, avoid special “low-carb” products that are full of carbs. This should be obvious, but creative marketers are doing all they can to fool you (and get your money). They will tell you that you can eat cookies, pasta, ice cream, bread and plenty of chocolate on a low-carb diet, as long as you buy their brand. They’re often full of carbohydrates. Don’t be fooled.