Intermittent Fasting: An Effective Strategy for Weight Loss and Body Fat Reduction?

Intermittent fasting (IF), also known as intermittent fasting, has gained popularity as a dietary approach that alternates periods of food intake with periods of fasting. Its main goal is to aid in weight loss and the elimination of body fat percentage, promoting a calorie deficit in a more flexible way than traditional diets. But does this strategy really deliver on its promises? Let’s explore what the latest scientific evidence says.

What is Intermittent Fasting?
IF is not a diet in the classic sense, as it does not restrict specific types of food, but rather the time of day when you eat. The most common protocols include:

16/8: 16-hour fast and 8-hour eating window (e.g., eating from 12 pm to 8 pm).
5:2: Normal eating for 5 days a week and severe calorie restriction (500-600 kcal) on 2 non-consecutive days.
Alternate-day fasting: Alternate days of total or modified fasting with days of free eating.

The main mechanism is to create a negative energy balance: during fasting, the body depletes glycogen reserves and begins to burn fat as an energy source, promoting ketosis and autophagy (cellular cleansing).

Benefits for Weight Loss and Fat Reduction
Studies indicate that IF can lead to a weight loss of 3% to 8% over periods of 8 to 12 weeks, mainly due to the natural reduction in calorie consumption. A review of clinical trials showed that protocols such as 16/8 or 5:2 result in an average loss of 1-2 kg per month, with a significant reduction in body fat, including visceral fat (that around the organs, associated with metabolic risks).
More recent research, including meta-analyses from 2025, confirms that IF is effective in reducing abdominal circumference, body fat percentage, and markers such as LDL cholesterol and triglycerides. In some cases, such as alternate-day fasting, there is greater weight loss (about 1.3 kg more) compared to continuous calorie restriction. In addition, it can improve insulin sensitivity, reduce inflammation, and even benefit gut and brain health.
Important: fat loss occurs primarily because people consume fewer calories in total, not through an accelerated “magical burn.” Comparative studies show similar results to traditional calorie deficit diets.

Limitations and Comparison with Other Diets
Although effective, IF is not superior to conventional calorie-restricted diets for long-term weight loss or fat reduction. A large study published in the New England Journal of Medicine and systematic reviews from 2025 conclude that there are no significant differences in body composition (fat vs. lean mass) when compared to balanced diets.
A critical point: in some protocols, there is a higher risk of muscle (lean) mass loss, which can slow down metabolism and be counterproductive for healthy weight loss. To minimize this, combining IF with strength training and adequate protein intake is essential.
Risks and Contraindications
IF is not for everyone. Common side effects include initial hunger, irritability, fatigue, and, in rare cases, hypoglycemia (especially in diabetics). It is not recommended for pregnant women, breastfeeding women, frail elderly people, people with eating disorders, low weight, or conditions such as type 1 diabetes without medical supervision.
Long-term studies are still limited, and there is debate about cardiovascular risks in extreme protocols. Always consult a nutritionist or doctor before starting.
Conclusion
Intermittent fasting is a valid tool to aid in weight loss and body fat reduction, especially for those who find it difficult to count calories daily. Its benefits are real, but equivalent to those of a balanced diet with a calorie deficit. Success depends on sustainable adherence, food quality during eating windows, and combination with healthy habits. It’s not a miracle solution, but it can be a practical and effective option when done with professional guidance. If the goal is long-term health, focus on the overall balance of the diet, not just fasting.