Over the last ten years, intermittent fasting has become a widely used approach to weight loss. This dietary program involves taking breaks of varying lengths between meals. Unlike other diets, there is no need to count calories or cut carbohydrates at all costs. While a balanced diet remains important, intermittent fasting focuses mainly on changing eating habits rather than changing what you eat. However, intermittent fasting must be practised with rigour and caution, possibly after consulting a doctor or nutritionist. While the benefits of this approach can be numerous, it can also pose health risks. Find out everything you need to know about intermittent fasting: the different types of diets, health benefits, side effects, and its true effectiveness. Everything you need to start (or not) your fast under the best possible conditions.
Intermittent fasting: what is it?
Fasting involves refraining from solid and/or liquid foods that provide nutrients. This ancient practice can be motivated by various reasons: religious, spiritual, philosophical, athletic, or health-related. In recent years, fasting has gained renewed interest, especially for its potential benefits for weight loss. That is how intermittent fasting originated in the United States. The principle? Alternate periods of eating with periods of not eating. During these phases, the body first uses its glycogen (sugar) stores in the liver and muscles, then draws on other reserves, such as fat, to keep functioning. During fasting hours, it is possible—and even recommended—to drink non-caloric beverages (water, unsweetened tea, black coffee). This approach, now popular worldwide, is mainly intended for people who are overweight or who have metabolic issues. While some health professionals recommend using this method for a specific period, it can also be adopted long term, under certain conditions. For example, it is possible to fast for several days, weeks, months, or even years, provided you are well prepared and supported.
14/10, 16/8: The different types of intermittent fasting
The fasting period can be shorter or longer, and more or less strict, depending on the method chosen. In fact, there are different types of intermittent fasting. First, there are the 12/12 (12 hours without eating) and 14/10 (14 hours without eating) fasts, recommended for beginners. The 16/8 fast, which involves an 8-hour eating window followed by 16 hours of fasting, is the most common because it fits well with many lifestyles. There are also three more intensive methods: 5/2 fasting, which involves eating normally for 5 days and then drastically reducing calories over the next 2 days (500 calories per day for women and 600 calories per day for men), “alternate day fasting”, which means fasting every other day, and “eat-stop-eat”, which means fasting for 24 hours once or twice a week. The type of intermittent diet you choose depends not only on your goals, but also on your fitness level and lifestyle.
Weight loss, cellular cleansing: the benefits of intermittent fasting
Intermittent fasting can help with weight loss, but it also has other therapeutic effects. Many researchers have studied intermittent diets and how they improve health and metabolism. While not all have reached definitive conclusions, several benefits have been observed. For example, intermittent fasting can give the digestive system a break, help you reconnect with feelings of fullness, increase the production of growth hormones, promote cell renewal, strengthen the immune system, and lower blood sugar levels. Reported effects of fasting also include a reduction in abdominal fat, increased energy, improved concentration, and lower stress levels. While intermittent fasting offers health benefits, it is not more effective than traditional diets. The difference is that it can feel less restrictive. However, intermittent fasting must be combined with a healthy, balanced diet. “People who continue to eat an unbalanced diet during the permitted period will not experience the expected benefits”, according to Jérôme Caradec, dietician-nutritionist.
Eating disorders, heart health: the risks of intermittent fasting
While intermittent fasting has many benefits, health professionals also highlight several drawbacks and adverse effects associated with this practice. Intermittent fasting can cause headaches and dizziness, limit social life, and trigger or worsen eating disorders. Digestive issues, nutritional deficiencies, and inflammation are sometimes observed in people who fast without proper supervision. One of the most serious risks associated with this diet involves heart health. In principle, intermittent fasting lowers cholesterol and triglycerides, which should improve cardiovascular health. However, a large-scale study analyzing data from over 20,000 adults found that people who limit their eating to less than eight hours a day had a 91% higher risk of dying from cardiovascular disease. This is why the Institut Pasteur warns against drastic methods, such as 5/2 and “eat-stop-eat”. Once again, a balanced diet is essential to reduce the risks of intermittent fasting.
Intermittent fasting is not for everyone
Intermittent fasting is not for everyone. It is contraindicated for young children, whose energy needs are high and reserves are low. It also requires treatment adjustments for people with diabetes who use insulin. Older adults, people with anemia, pregnant and breastfeeding people, high-performance athletes with high protein and carbohydrate needs, and people with eating disorders should not practise it. Outside of these situations, a healthy adult can practise it with medical supervision or personalized nutritional follow-up. However, it remains important not to turn this practice into a constraint. Don’t be too demanding or harsh with yourself. Listen to your body, and allow yourself to break your fast if necessary.
