How Fast Can You Lose Weight Fasting? A Study Reveals the Shocking Truth

Water fasts, where individuals consume only water for several days, can potentially lead to weight loss, but the duration of this weight loss is uncertain, according to new research from the University of Illinois Chicago. The study also indicated that other metabolic benefits associated with water fasts, such as reduced blood pressure and improved cholesterol levels, appear to diminish rapidly after the fasting period concludes. For those wondering can fasting make you lose weight, this research provides valuable insights into the speed and sustainability of results.

Krista Varady, a professor of kinesiology and nutrition who spearheaded the research published in Nutrition Reviews, noted that while water fasts or similar very-low-calorie fasts don’t seem to cause severe adverse effects, their benefits might be short-lived.

“My overall conclusion is that I guess you could try it, but it just seems like a lot of work, and all those metabolic benefits disappear,” Varady stated. She emphasized the critical need for medical supervision for anyone considering such a fast for longer than five days.

Varady, recognized as an expert on intermittent fasting, explained her motivation for studying water fasting stemmed from increased media inquiries last fall. She decided a review of existing research was necessary before offering comment. If you’re exploring options like how to lose weight rapidly in 1 week, understanding the nuances of different fasting methods is crucial.

The Study’s Findings on Weight Loss Speed

The paper represents a comprehensive literature review encompassing eight studies focused on water fasting or Buchinger fasting – a medically supervised fast common in Europe involving minimal consumption of juice and soup. Varady’s team analyzed the cumulative results from these studies to assess the impact of these fasts on weight loss and various metabolic indicators.

The researchers observed that fasting did indeed stimulate notable short-term weight loss. Participants who fasted for five days typically lost about 4% to 6% of their body weight. For those undertaking fasts lasting seven to 10 days, the weight loss ranged from approximately 2% to 10%. Longer fasts of 15 to 20 days resulted in a weight reduction of 7% to 10%. These figures offer a direct answer to the question of can you lose weight from fasting, showing that initial rapid loss is possible.

The Catch: Weight Regain and Fading Benefits

However, only a limited number of the reviewed studies tracked whether participants regained the lost weight once they stopped fasting. In one instance, individuals on a five-day water fast regained all the weight they had lost within just three months. Two other studies reported only minor weight regain, but these involved participants who were specifically encouraged to restrict calorie intake after the fasting period ended. This suggests that while you might achieve quick results asking can i lose weight by fasting, maintaining that loss is a separate challenge.

It became evident that the metabolic improvements seen during the fasts were temporary. Positive changes in blood pressure, cholesterol, and blood sugar levels quickly reverted to baseline levels once participants resumed normal eating habits.

Some studies included individuals with Type 1 and Type 2 diabetes who participated without ill effects, although they received close monitoring and insulin adjustments during fasting.

Side Effects and Muscle Loss Concerns

Common side effects reported during these prolonged fasts were similar to those experienced with intermittent fasting, including headaches, insomnia, and hunger. The studies reviewed did not report any serious negative outcomes like metabolic acidosis or fatalities.

Krista Varady, expert researcher on fasting and weight loss studies

A significant finding was that participants undergoing these prolonged fasts lost roughly two-thirds of their weight from lean mass (muscle) and only one-third from fat mass. This pattern is the reverse of typical weight loss scenarios where more fat is lost than muscle. Varady explained that this occurs because “your body needs a constant intake of protein. If it doesn’t have that, then it draws from muscles.”

Varady’s broader research on intermittent fasting has explored its effectiveness for weight loss and specific concerns like its impact on fertility, finding no detrimental effects in that area. For many, the question becomes is intermittent fasting good for weight loss compared to more extreme methods.

Expert Recommendation: Intermittent Fasting

Varady, also affiliated with the University of Illinois Cancer Center, suggested that individuals aiming for weight loss might find more sustainable success with intermittent fasting rather than a water fast. “There’s a lot more data to show it can help with weight management,” she noted.

Other researchers involved in this study included Sofia Cienfuegos, Shuhao Lin, Vasiliki Pavlou, and Kelsey Gabel, along with former UIC student Mark Ezpeleta.

In conclusion, while studies indicate that water fasting can lead to rapid short-term weight loss, the research suggests this loss may not be sustained, and the associated metabolic health benefits are fleeting once normal eating resumes. The significant loss of lean muscle mass is also a notable concern. Experts like Krista Varady propose intermittent fasting as a potentially more manageable and better-supported strategy for long-term weight management.