Fasting May Help You Lose Weight Quickly, But It Can Return Just As Fast
Let’s face it. Water is not a meal. While it may be tempting to fast for many days and drink nothing but water to lose weight, it’s unknown how long those pounds will stay away. Research from the University of Illinois Chicago suggests that other metabolic perks including reduced blood pressure and improved cholesterol may also fade away once the fast ends.
The good news is that serious negative side effects have not been observed in individuals doing water or other type of low-calorie fast, according to Krista Varady, professor of kinesiology and nutrition, who led the research published in Nutrition Reviews.
She notes that people could try it though it seems arduous and metabolic benefits go away. Varady advises to not continue these fasts for more than five days and they should be medically supervised.
Varady is an expert on intermittent fasting and wanted to research water fasting because she was receiving frequent requests from journalists about the diet. Her recent research is a literature review of eight studies on fasting or Buchinger fasting, a popular European fast that’s medically supervised. Individuals eat only a tiny amount of juice and soup each day. Varady’s researchers evaluated the results of each of the papers to see what they collectively say about fasting and weight loss as well as other metabolic parameters.
Fasting initially showed impressive short-term weight loss. Individuals who fasted for five days lost between 4 and 6% of their weight. Those who fasted for seven to ten days lost between 2 and 10%. For those that fasted for 15 to 20 days, a 7 to 10% weight loss was observed.
In a handful of studies in the review, some tracked subjects’ weight gained back after they ended their fasts. One study found that people gained all the weight that was lost in a 5-day water fast within three months. In two studies, participants were advised to restrict calories after the fasts stopped, and a minimal amount of lost weight was regained.
The metabolic benefits of fasting were gone soon after the fasts stopped. Reductions in blood pressure, cholesterol, and blood sugar were seen briefly but returned to baseline levels once subjects started eating again.
Negative effects were not seen in studies that included subjects with Type 1 and Type 2 diabetes. These participants were watched closely and their insulin doses were tweaked during fasting.
Side effects of prolonged fasts were similar to those seen during intermittent fasting including headaches, insomnia, and hunger. Metabolic acidosis and/or death did not occur, according to Varady.
Weight loss in the participants was two-thirds lean mass and one-third fat mass. This is counter to regular, slow weight loss where more fat is lost than lean muscle. Varady notes this makes sense because, "your body needs a constant intake of protein. If it doesn't have that, then it draws from muscles."
Her research reviewed how well intermittent fasting works for weight loss and certain questions such as if intermittent fasting impacts fertility, which it does not. She advises intermittent fasting over water fasting, "because there's a lot more data to show it can help with weight management," she said.
Below are some safe, simple tips for weight loss:
1. Pass on water fasts as most of the weight loss is muscle loss.
2. Eat breakfast. According to the National Weight Control Registry, successful losers eat breakfast. 2
3. Make dinner your last meal and skip the evening snacks.
4. Include high-protein foods with meals and snacks. These provide satiety and have been found to help with preventing weight regain. 3
5. Swap low-fiber carbs for high-fiber carbs such as rolled oats, brown rice, whole-grain pasta or bread, and quinoa.
6. Add more vegetables to meals for more volume without extra calories.
7. Skip soda, sports drinks, and other high-calorie sugary beverages.
8. Limit fast food, fried foods, and high-calorie desserts.
9. Get to bed at a reasonable time and aim for 7 to 8 hours of sleep. Sleep is good food and may help reduce cravings for comfort food.
10. Include movement in your everyday life. Walking can be done anytime, anywhere.
Lisa Andrews, MED, RD, LD
References:
Mark Ezpeleta, Sofia Cienfuegos, Shuhao Lin, Vasiliki Pavlou, Kelsey Gabel, Krista A Varady. Efficacy and safety of prolonged water fasting: a narrative review of human trials. Nutrition Reviews, 2023; DOI: 10.1093/nutrit/nuad081
Martínez-Gómez MG, Roberts BM. Metabolic Adaptations to Weight Loss: A Brief Review. J Strength Cond Res. 2022 Oct 1;36(10):2970-2981. doi: 10.1519/JSC.0000000000003991. Epub 2021 Mar 3. PMID: 33677461.
