Intermittent fasting that restricts calories three days a week leads to significantly better weight loss than daily calorie counting, according to groundbreaking research from the University of Colorado.
At a Glance
- A 12-month study found 4:3 intermittent fasting produced 7.6% weight loss versus 5% with traditional daily calorie restriction
- The fasting group had better adherence with only 19% dropping out compared to 30% in the calorie-counting group
- Participants following intermittent fasting showed greater improvements in blood pressure, cholesterol, and glucose levels
- The 4:3 approach allows normal eating four days a week while restricting calories by 80% on three non-consecutive days
A New Approach to Weight Loss
Researchers from the University of Colorado School of Medicine have provided compelling evidence that intermittent fasting may be more effective than traditional dieting for weight loss. The randomized clinical trial involved 165 adults with overweight or obesity who were assigned to either a 4:3 intermittent fasting regimen or daily calorie restriction for 12 months. Both groups received identical support, including behavioral guidance, calorie counting instruction, a free gym membership, and encouragement to exercise at least 300 minutes weekly.
The 4:3 intermittent fasting approach required participants to reduce their calorie intake by 80% on three non-consecutive days each week, with no restrictions on the other four days. Meanwhile, the calorie restriction group followed a traditional diet with a daily calorie goal designed to create a 34.3% energy deficit. This study, published in the Annals of Internal Medicine and funded by the National Institutes of Health, offers significant insights for adults struggling with conventional weight loss methods.
A recent study by #CUAnschutz researchers showed that 4:3 intermittent fasting resulted in modestly greater weight loss than daily caloric restriction over 12 months. The results were published in @AnnalsofIM. ????️ https://t.co/YvrBd1kkbT
— CU Anschutz Medical Campus (@CUAnschutz) April 1, 2025
Superior Results and Better Adherence
After one year, the results clearly favored the intermittent fasting approach. The 4:3 group achieved an average weight loss of 7.6% of their body weight, compared to just 5% in the daily calorie restriction group. Moreover, 58% of participants in the fasting group achieved at least 5% weight loss, versus 47% in the calorie restriction group. These differences are particularly meaningful considering that a 5% weight reduction is often associated with significant health improvements.
Perhaps more telling than the weight loss figures was the difference in program adherence. Only 19% of participants in the intermittent fasting group dropped out during the study, compared to 30% in the daily calorie-counting group. This suggests that many people find it easier to restrict calories severely for just three days per week rather than moderately every day. The intermittent approach may reduce the mental fatigue associated with constant food monitoring and restriction.
Health Benefits Beyond Weight Loss
The advantages of the 4:3 fasting approach extended beyond just weight reduction. Participants in the fasting group experienced more favorable changes in important cardiometabolic markers, including blood pressure, cholesterol levels, and fasting glucose levels. These improvements suggest that intermittent fasting may offer additional health benefits that could reduce the risk of heart disease and type 2 diabetes, conditions that are particularly concerning for adults over 40.
Researchers emphasized that the 4:3 intermittent fasting approach differs from time-restricted eating, which limits daily food intake to a specific window but doesn’t necessarily reduce overall calories. For those interested in trying intermittent fasting, the study authors recommend starting with just one fasting day per week and gradually increasing to three days to allow the body to adjust. This gradual approach may help minimize potential side effects like hunger, irritability, or headaches that can occur during initial fasting periods.
Limitations and Future Research
Despite the promising results, researchers acknowledge several limitations. The study relied on self-reported food intake, which could affect the accuracy of the results. Additionally, the findings may not apply to all demographic groups, as study participants represented a specific population. This highlights the importance of personalized approaches to weight management, as different strategies may work better for different individuals based on their unique circumstances, preferences, and health status.
Looking ahead, researchers are exploring the potential benefits of 4:3 fasting for specific groups, including breast cancer survivors and people with chronic conditions. They also aim to develop more accessible programs that could be implemented in clinical and community settings. A long-term follow-up study is planned to identify which individuals are most likely to succeed with intermittent fasting and to better understand the biological mechanisms behind its benefits. For now, this research offers a promising alternative for adults seeking effective weight management strategies.
Sources:
https://medicalxpress.com/news/2025-04-intermittent-fasting-modestly-greater-weight.html
https://www.aol.com/4-3-intermittent-fasting-beats-200700682.html
