Can Fasting Make You Lose Weight? Study Shows Short-Term Gains, Quick Regain
Water fasts, which involve consuming only water for several days, might offer short-term weight loss results, but maintaining that loss over time appears challenging, according to new research from the University of Illinois Chicago. The study also indicates that other potential metabolic benefits, such as improvements in blood pressure and cholesterol levels, seem to disappear soon after the fasting period concludes.
However, those who undertake a water fast or a similar very low-calorie fast generally do not experience serious adverse effects, noted Krista Varady, professor of kinesiology and nutrition and lead researcher on the study published in Nutrition Reviews.
“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, emphasizing the need for medical supervision for fasts lasting longer than five days. While water fasting might offer a route on how to lose weight fast in 2 months, the long-term effectiveness for maintaining that loss remains a key challenge.
Exploring Extreme Fasting: Research Insights
As an expert on intermittent fasting, Varady was prompted to investigate water fasting following increased media inquiries about its effectiveness and safety. Her team’s work involved a literature review of eight studies focusing on either water fasting or Buchinger fasting, a supervised fasting method popular in Europe that permits minimal juice and soup intake daily.
Dr. Krista Varady, expert on intermittent fasting, discusses water fasting research
The review examined the cumulative impact of these fasts on weight loss and various metabolic factors.
Weight Loss Results and Regain
The research confirmed that fasting does lead to noticeable short-term weight reduction. Participants fasting for five days lost approximately 4% to 6% of their body weight, while those fasting for seven to 10 days lost about 2% to 10%. Longer fasts of 15 to 20 days resulted in a 7% to 10% weight loss.
However, few studies in the review tracked participants after the fast ended. In one instance, individuals regained all lost weight from a five-day water fast within three months. In others, less weight returned, but participants followed calorie-restricted diets post-fasting. The temporary nature of the results contrasts with desires like lost 10 pounds in a week without trying and keeping it off permanently. For those considering aggressive short-term goals like can you lose 20 pounds in a week, the study indicates initial loss is possible but likely not sustainable without post-fasting intervention.
Transient Metabolic Benefits
Crucially, the metabolic health benefits observed during the fasts quickly dissipated. Improvements in blood pressure, cholesterol, and blood sugar levels reverted to baseline shortly after participants resumed normal eating patterns.
Safety Profile and Side Effects
Participants with Type 1 and Type 2 diabetes were included in some studies and experienced no adverse effects, benefiting from close monitoring and insulin dose adjustments.
Common side effects of prolonged fasts mirrored those of intermittent fasting, including headaches, insomnia, and hunger. The reviewed studies reported no severe negative outcomes like metabolic acidosis or death. Understanding the composition of loss, particularly how to lose inches fast in a week, is key; the study noted that two-thirds of the weight lost during these extreme fasts was lean mass, and only one-third was fat mass – the opposite of typical weight loss patterns. This is attributed to the body needing a constant protein supply, drawing from muscles when intake is absent.
Intermittent Fasting as an Alternative
Varady, whose prior research includes examining whether intermittent fasting affects fertility (finding it does not), suggests intermittent fasting as a potentially more sustainable approach for those seeking weight management.
She recommends intermittent fasting over extreme fasts like water fasting because “there’s a lot more data to show it can help with weight management.” Considering options like lose 7 pounds in 2 weeks without trying, intermittent fasting might offer a more balanced path compared to prolonged, restrictive fasting methods with less evidence for long-term success.
Other researchers involved in the study included Sofia Cienfuegos, Shuhao Lin, Vasiliki Pavlou, Kelsey Gabel, and former UIC student Mark Ezpeleta.
Conclusion
While extreme fasts like water fasting can indeed make you lose weight rapidly in the short term, the research indicates that this weight loss is often quickly regained, and associated metabolic health benefits are temporary. The study highlights that prolonged fasting leads to significant lean mass loss and carries side effects similar to intermittent fasting without demonstrating superior long-term health outcomes or sustainable weight management compared to less extreme methods like intermittent fasting, which is recommended by the expert researcher based on available data.
