5 People Who Should Never Try Intermittent Fasting, Says a Dietitian
Intermittent fasting (IF) has been a weight-loss method many individuals have turned to. It involves an alternating eating and fasting pattern with a goal of weight loss, better metabolic wellness, and reduced inflammation. Some common patterns include fasting for 16 hours and restricting food intake to an eight-hour window. Others assume their regular eating pattern for five days straight, then limit their calorie intake to between roughly 500 and 600 for two consecutive days.
While positive results can be achieved from IF, there are also risks. If you are pregnant or have certain chronic conditions, intermittent fasting is not a viable choice for you. To learn more about this weight-loss method, we spoke with Ana Reisdorf, MS, RD, Registered Dietitian and Founder at GLP-1 Hub, who shares why she tells certain clients to avoid IF altogether.
How IF Impacts Metabolism and Muscle Mass
For those in their 40s, 50s, and beyond, IF can make it challenging to meet daily protein needs, which can lead to increased muscle loss. This is concerning, as muscle mass already naturally decreases with age. In addition, it can decrease metabolic rate and increase cortisol (the stress hormone) over time.
Who Shouldn’t Intermittent Fast
While IF can be a successful method for some—and there’s a ton of supporting research behind its benefits—it’s not the right path for everyone.
“In those with hormonal changes (menopause/perimenopause), high stress, or on GLP-1s, fasting can cause calorie/protein intake to drop too low, increasing fatigue, muscle loss, or hormonal dysregulation,” says Reisdorf.
Who’s More Likely To Experience Negative Effects
According to Reisdorf, women in menopause and perimenopause, those who have diabetes (especially type-1), those with greater nutritional requirements (i.e. athletes), and individuals taking GLP-1 medication are most likely to experience negative side effects of IF.
“These groups have higher protein needs, hormonal imbalances, and can’t really afford to underfuel,” Reisdorf explains.
How Common It Is To Experience Setbacks With IF
Experiencing setbacks with IF is quite common, particularly in women who aren’t already consuming sufficient calories or those under significant stress.
“Many don’t realize they’re not eating enough because of IF until they feel exhausted, their hair starts falling out, they lose muscle, or weight loss completely stalls,” Reisdorf points out.
Mental and Behavioral Challenges You May Face When Fasting
IF typically increases obsessive thoughts about food, rebound overeating, and “black and white thinking” around eating habits.
“For some, IF makes an all-or-nothing mindset worse,” Reisdorf says.
If you’re curious about what else GLP-1s can do, check out 5 Surprising Health Benefits of GLP-1 Drugs That Have Nothing to Do With Weight Loss.