Under Eating Warning on GLP-1

In the most recent Fat Science episode, Dr. Emily Cooper and her colleagues tackle a tricky but crucial topic: eating too few calories while on meds like Zepbound or Ozempic.

This caught my attention. We know GLP-1 medications affect everyone differently. For some, appetite drops so drastically that they can barely eat, sometimes consuming less than 1,000 calories a day.

That kind of drop is often celebrated as a win, a sign the meds are "working." But that's a flawed understanding of both the medication and how metabolism really works.

Here's what I learned from the podcast episode.

The Counter-Intuitive Eating Strategy

Mindful or intuitive eating is a common message from dietitians. The basic idea is to eat only when you're hungry and stop when you're full.

However, GLP-1 medications can suppress your body's natural hunger signals. And because these drugs interfere with appetite cues, relying on intuition alone can lead to consistently eating too little. Over time, this may cause muscle loss, fatigue, unstable blood sugar and make the medication less effective.

If hunger signals can't be trusted while on GLP-1s, how should you approach eating? Dr. Cooper advocates for what she calls "Mechanical Eating".

This means eating on a schedule throughout the day (e.g., every few hours) and including all food groups, regardless of intense hunger or fullness. Why? Because even if your brain isn't screaming for food, your body still needs consistent fuel to function optimally, preserve muscle mass, and keep your metabolism humming. It's about consciously providing the necessary building blocks when your natural signaling system is altered.

Under-Fueling Has Real Consequences

Eating too little, around 1200 to 1400 calories a day, might seem to work at first. Your body starts using fat for fuel. Hunger fades. It thinks you have eaten. For a while, that feels like success.

But longterm under-fueling sends a signal of scarcity, prompting your metabolism to slow down. Hormones like leptin start to react. They tell your brain something is wrong. They say you are not eating enough. Over time, this can hurt your progress. It can drain your energy, affect your mood and stall your weight loss.

Dr. Cooper explained: "Even before I got into working with people with high body weight, what I noticed when I did metabolic testing in athletes... it's the more that you would eat, the faster your metabolic rate would go, basically. And the less you would eat, it just adapts and slows down to that level."

This metabolic adaptation is precisely what makes severe calorie restriction counterproductive. When you drastically reduce calories, your body doesn't just continue burning energy at the same rate - it downshifts your entire metabolic system to conserve resources.

No Hunger Eating Plan

Set reminders to eat every three to four hours, even if you're not feeling hungry. Your body still needs regular fuel to function well.

Make lean protein a key part of every meal to help preserve muscle as you lose weight. Since you're likely eating less, choose foods that give you the most benefit.

Fill your plate with vegetables, fruits, whole grains, and healthy fats to keep your nutrition strong and your energy steady.

By the way, one of the most popular posts on this blog is about Meal Planning on GLP-1. A lot of people find this part overwhelming. It feels like too much effort on top of everything else. But it does not have to be complicated. All you really need is a simple structure that fits into your life. That is exactly what we explore in that post.

The message from doctors is clear: don't let appetite suppression lead to undereating. Your body needs proper fuel to function optimally. Focus on finding the right balance to support metabolic health, maintain muscle and achieve lasting well-being.

If strong appetite suppression has caused you to shift toward overeating, consider adopting mechanical eating with set reminders to stay on track.

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