January 2025
FASTING AS A HEALTH SOLUTION? NOT SO FAST
Recent research on time-restricted eating shows it works well for weight loss but isn’t as promising as scientists once hoped.
Intermittent fasting probably isn’t the health hack you hoped it would be. More studies suggest that for a small subset of people it can help you lose weight but likely isn’t a silver bullet for other health improvements like lowering your inflammation levels or lengthening your lifespan. And some evidence suggests fasting can make it more difficult to build and retain muscle. People were hoping that this would be a magical thing that offered amazing results for them. All it does for some is help them eat less. The popularity of intermittent fasting exploded starting around 2010. The most popular type is time-restricted eating, which involves eating meals within a limited time frame each day. It’s the easiest for most people to stick to, and can be as simple as eating dinner at 5 PM and not eating again until the next morning. Early research in animals suggested that it could reduce the risk of developing heart disease and certain types of cancer, and potentially extend your lifespan. But limited research in humans and disappointing results have muted some hopes.
Time-restricted eaters consume on average between 200-500 fewer calories a day, some studies suggest. Some participants lost weight, from less than 1% to roughly 8% of total body weight. Aside from a small improvement in the body’s processing of glucose, the fasters didn’t show benefits in health and longevity markers such as inflammation levels. At the same time, doctors and intermittent fasters themselves say skipping meals makes it difficult to eat enough protein or maintain their muscle mass. Time-restricted eaters lost roughly twice as much lean mass, the body’s nonfat weight, as fat mass compared with a control group. Some health experts say intermittent fasting can be a helpful weight-loss tool for some, but for others, the hunger during fasting period will lead to extra snacking during their eating periods. And when it comes to overall health, what people eat is much more important then when they eat.
In recent years, several big names in health and wellness have reigned in or abandoned their fasting regimens, in part citing concerns around protein and muscle mass. Some used to do prolonged fasts, believing this practice would stimulate a cellular recycling process called autophagy that declines with age. Dr. Peter Attia, physician and author of Outlive, used to fast for 3 days per month, and up to 10 days every 3 months. He has now stopped this practice because of lean mass loss and a lack of scientific understanding about how to measure the benefits. Dr. Brad Stanfield, a New Zealand-based primary care physician who runs a preventive medicine YouTube channel, stopped daily time-restricted eating after reviews failed to failed to find health benefits. Other health experts and elite athletes have also abandoned the practice after noticing feeler weaker and experiencing injuries in quick succession. For others, the fixation on intermittent fasting can feel like an eating disorder.
The science on intermittent fasting is ever developing. Much of it began with studies of calorie restriction in animals. Most studies in humans are relatively small, short-term, and often limited to specific groups of people, like those with diabetes or obesity. While scientists continue to research the risks and benefits of this regimen, there are probably more benefits to keeping an earlier eating window rather than later. As the old adage goes, “Eat breakfast like a king, lunch like a prince and dinner like a pauper.”
Alex Janin
**Intermittent fasting is NOT advised for those with diabetes, pre-diabetes/insulin resistance, morbid obesity or those who are elite athletes. Please carefully discuss any plans you have for this regimen with either your physician or registered dietitian.