Intermittent fasting (IF) is an eating pattern that cycles between periods of eating and fasting. Unlike traditional diets that focus on what you eat, intermittent fasting focuses on when you eat. The approach has gained significant popularity for weight loss, and research supports some of its benefits — but like any strategy, it has important limitations, especially for patients on GLP-1 medications.
16:8 (time-restricted eating): The most popular approach. You eat during an 8-hour window and fast for the remaining 16 hours. For most people, this means skipping breakfast and eating between noon and 8 PM, though the window can be adjusted to fit your schedule.
5:2 method: You eat normally five days per week and restrict calories to 500-600 on the remaining two non-consecutive days.
Alternate day fasting: You alternate between regular eating days and fasting or very-low-calorie days. This is more aggressive and harder to sustain long-term.
Intermittent fasting primarily works by reducing total caloric intake. By limiting the hours during which you eat, most people naturally consume fewer calories. There's also evidence that fasting periods may improve insulin sensitivity, increase cellular repair processes, and modestly enhance fat oxidation — though the magnitude of these metabolic benefits beyond simple caloric restriction is still debated in the research.
Patients taking semaglutide or tirzepatide are already experiencing significant appetite suppression. Adding a restrictive eating window on top of medication-induced appetite reduction can make it very difficult to consume adequate protein and nutrition within the limited eating hours. This can accelerate muscle loss and nutritional deficiencies — the very outcomes our program is designed to prevent.
Benefits: For patients not on appetite-suppressing medications, IF can be an effective structure for reducing caloric intake without counting calories. Some people find it simpler than tracking macros — you just don't eat during certain hours. Research also suggests potential benefits for metabolic health markers, including blood sugar regulation and inflammation.
Limitations: IF doesn't address what you eat, only when. A poor diet compressed into an 8-hour window is still a poor diet. Compliance can be difficult long-term, particularly in social settings. And for patients who need high protein intake to preserve muscle mass during weight loss, a restricted eating window can make it harder to hit their targets.
As with all nutritional strategies, our nutrition team evaluates whether intermittent fasting makes sense for each patient individually. For some — particularly those who aren't taking GLP-1 medications — a time-restricted eating pattern can be a useful framework. For others, the priority is maximizing nutrient quality and protein intake during every available eating opportunity. Your provider helps you find the approach that serves your goals without compromising your health.