The traditional method of counting calories to achieve weight loss has often proven to be a time-consuming and disappointing process. However, there is an alternative approach called intermittent fasting, with the popular variation known as time-restricted eating. This method offers a simpler option for individuals aiming to reach a healthy weight. The question remains: is intermittent fasting more effective than calorie counting for losing weight? A recent study published in the Annals of Internal Medicine sought to provide an answer by comparing the two methods. The study concluded that both approaches can be equally effective if undertaken with professional counseling.
The year-long study conducted at the University of Illinois Chicago involved 90 adults with obesity, aged 18 to 65. These participants were randomly assigned to one of three groups: a time-restricted eating group, a daily calorie restriction group, and a control group. The time-restricted eating group was required to consume all their calories between noon and 8 pm, while the daily calorie restriction group had to reduce their calorie intake by 25% by closely monitoring their diet. The control group maintained their normal eating patterns.
In the first six months, both groups lost approximately 5% of their initial body weight. To sustain this weight loss, the diets were adjusted accordingly over the next six months. The time-restricted eating group extended their eating window to ten hours (10 am to 8 pm), while the daily calorie restriction group increased their calorie intake to match their requirements. The control group continued their regular eating pattern.
The study examined the effects of these diets on body composition, waist circumference, and various health markers. It was found that both restricting the time during which individuals could eat and reducing calorie intake were equally effective for weight loss. After 12 months, participants in both groups lost about 4% of their starting body weight. Both diets also resulted in reduced waist circumference and fat mass to a similar extent. Interestingly, despite the different approaches, calorie intake was reduced to a similar extent with both methods.
No significant changes were observed in health markers such as glucose, insulin, or cholesterol levels. This may be due to the use of a later time-restricted eating window (12 pm to 8 pm), which was considered more acceptable for participants. Previous studies have suggested that an early time-restricted eating window (e.g., 8 am to 4 pm) can lead to greater weight loss and improved blood glucose regulation. The reason behind this is not yet fully understood, but research suggests that our metabolism is more efficient earlier in the day, aligning with our natural waking and sleeping patterns.
Implications and Considerations
These findings support previous studies comparing time-restricted eating and other forms of intermittent fasting, such as the 5:2 diet, to daily calorie restriction. The key factor in weight loss, regardless of the method used, is calorie restriction. The study also highlighted the racial diversity of the participants, with 79% being black or Hispanic, making the results more applicable to a wider population.
However, it is important to note that participants in both dietary intervention groups received significant counseling throughout the study. This included guidance on healthy eating and cognitive behavioral therapy to reduce impulse eating. The inclusion of this counseling may have helped participants resist the urge to consume high-calorie foods after completing their fasting window. Therefore, it is unclear whether the effectiveness of time-restricted eating and daily calorie restriction alone can be attributed solely to these interventions or if professional support with healthy eating is necessary.
Interestingly, a recent study found that time-restricted eating without additional support did not lead to weight loss after three months. Additionally, there were notable variations in weight loss among individual participants on each diet, suggesting that certain factors may make time-restricted eating or daily calorie restriction more effective for some individuals than others. Weight loss is undoubtedly challenging, regardless of the method employed. While intermittent fasting, specifically time-restricted eating, has shown promise for weight loss, individual outcomes may vary. The exact reasons behind these variances remain unknown.