Recent research shows that intermittent fasting (IF) can yield similar results to traditional calorie restriction (CR) when it comes to weight loss. In fact, one specific form of IF, known as whole-day fasting, appears to result in slightly greater weight loss than calorie-restricted diets.

Experts are suggesting that the similarity in outcomes between these different diet approaches offers flexibility for those looking to shed pounds, allowing them to choose the method that aligns best with their personal lifestyle.

Intermittent Fasting and Calorie Restriction Yield Similar Results

A comprehensive review of nearly 100 randomized clinical trials comparing intermittent fasting and traditional calorie restriction found that both methods resulted in similar improvements for weight loss and various cardiometabolic risk factors. Published on June 18 in The BMJ, the study revealed that both IF and CR were effective, although IF has garnered increasing attention in recent years.

Intermittent fasting (IF) involves alternating periods of eating and fasting, with less emphasis on what you eat and more focus on when you eat. In contrast, calorie restriction (CR) involves setting a daily calorie limit without altering the eating schedule. Among the common IF protocols explored in the study were:

• Alternate Day Fasting (ADF): A pattern that alternates between fasting days and regular eating days, often with very low-calorie consumption on fast days.

• Time-Restricted Eating (TRE): Involves eating all meals within a specific window, typically 8-12 hours.

• Whole-Day Fasting (5:2 Diet): A method that involves fasting for two or three non-consecutive days each week.

The review indicated that all forms of IF, as well as traditional CR, led to weight loss compared to an unrestricted diet. However, alternate-day fasting (ADF) produced slightly greater weight loss compared to calorie restriction (about 3 pounds more on average). Researchers caution that further long-term studies are needed to verify these results.

Finding the Right Approach to Weight Loss

David B. Sarwer, PhD, director of the Center for Obesity Research and Education at Temple University, noted that the main takeaway from this analysis is that the best weight loss approach is the one that fits your lifestyle. “This suggests that the best approach to losing weight is finding an approach that matches your lifestyle and is something you can practice for the long term,” Sarwer said.

While IF has surged in popularity over the past decade, its health benefits—including weight loss and improvements to metabolic health—have been inconsistently demonstrated compared to traditional calorie restriction. That said, both diets have shown comparable results, which is encouraging for individuals seeking a sustainable weight loss method that suits their preferences.

No One-Size-Fits-All Solution

The systematic review involved 99 clinical trials with over 6,500 adult participants. The average age of participants was 45, with two-thirds being women. A significant portion of the participants had existing health conditions, such as obesity or type 1 and type 2 diabetes, and most had a body mass index (BMI) of 31 or higher, indicating obesity.

The trials, which lasted anywhere from 3 to 52 weeks (with an average of 12 weeks), revealed that both IF and CR resulted in modest reductions in body weight. Among the different IF protocols, ADF showed a slight advantage in weight loss compared to CR. However, Sarwer emphasized that the additional weight loss seen with ADF was relatively minor and likely not significant enough to lead to substantial health improvements.

Interestingly, ADF also slightly outperformed TRE and whole-day fasting in terms of weight loss. ADF was also linked to improvements in cholesterol levels, particularly LDL (bad) cholesterol, when compared to time-restricted eating.

Sarwer summed up the findings by saying that there is no “best” diet for weight loss, as the most effective approach is the one that individuals can maintain over the long term. “The best approach is one where the person can make small, yet impactful changes to their food choices, eating behaviors, and physical activity that cause minimal disruption to their lifestyle,” he added.

Intermittent Fasting’s Potential Health Benefits

Despite the research showing comparable results between IF and CR, intermittent fasting has been linked to several other health benefits. These include:

• Weight loss: Of course, the most notable benefit of IF.

• Improved insulin resistance: Helping the body respond better to insulin, which is important for managing type 2 diabetes.

• Reduced inflammation: A crucial factor in various chronic conditions.

• Improved brain health: Some studies suggest that IF can protect against neurodegenerative diseases.

While IF is often promoted as a health miracle, the critical question remains: Is it better than calorie restriction? The answer is not entirely clear.

A 2024 review found that both IF and CR led to weight loss and offered similar benefits across multiple health outcomes, including cardiometabolic health and brain function. However, adherence to intermittent fasting was notably higher, suggesting people may find IF easier to stick to than traditional calorie-restricted diets.

A 2022 study in NEJM concluded that among individuals with obesity, time-restricted eating (TRE) didn’t show better results than calorie restriction. Yet, a 2025 clinical trial funded by the NIH found that participants practicing whole-day fasting lost 50% more weight than those on CR after one year—along with significant improvements in blood pressure, cholesterol, and A1C levels.

Adherence is Key for Long-Term Success

A key finding in this study was that adherence rates dropped significantly as trial lengths increased. In trials lasting less than 24 weeks, adherence was high (above 80%), but for those lasting longer than 52 weeks, adherence fell dramatically. In one study involving whole-day fasting, adherence plummeted from 74% at six weeks to just 22% at 52 weeks.

This points to the importance of finding a diet that is sustainable in the long run, tailored to the individual’s preferences and lifestyle. “I wish there was an easy solution to weight loss. In our society, there are many forces that push individuals toward weight gain,” said Dr. Sun Kim, an associate professor of Endocrinology at Stanford Medicine. She emphasized the importance of discussing lifestyle changes that can be maintained over time.

Sarwer also advocates for smaller, sustainable changes. “I’m more likely to suggest that people reduce the number of days a week that they eat ice cream or reduce the portion size they eat, rather than recommending that they stop eating ice cream altogether,” he said.

Who Should Be Cautious with Intermittent Fasting?

While intermittent fasting can offer significant health benefits, it’s not suitable for everyone. Those who should proceed with caution include:

• Individuals over the age of 65

• People with a history of disordered eating

• Those with low blood pressure

• Pregnant or nursing women

• People with diabetes, especially those who take insulin (due to potential adjustments needed to insulin dosage and timing)

Final Thoughts

Ultimately, both intermittent fasting and calorie restriction have their merits. The best approach to weight loss and improved health is the one that fits your unique lifestyle and is sustainable over time. While one method might work better for some people, the key is sticking with it and making gradual, lasting changes that support long-term health goals.