This week on Fat Science, Dr. Emily Cooper, Mark Wright, and Andrea Taylor break down two GLP-1 studies that challenge a major media myth: GLP-1 medications don’t drive weight loss just because people eat less. Instead, drugs like tirzepatide and semaglutide create direct metabolic shifts—including increased fat oxidation and improved fuel partitioning—regardless of appetite.

The team also explores mechanical eating, the psychological impact of “diet food,” and Andrea’s 13-year metabolic recovery journey.

Key Questions Answered

• If both groups are dieting, why does the tirzepatide group lose more weight?
• What is metabolic adaptation, and why does dieting slow metabolism so sharply?
• How do GLP-1s directly increase fat oxidation?
• What is mechanical eating, and why do GLP-1 users need it?
• Why does ad-lib eating produce different metabolic responses than calorie restriction?
• Can mindset alone change hunger hormones? (Yes—the milkshake study.)
• Why do diet foods and diet sodas fail to improve metabolic health?
• Why is response to GLP-1s so different from person to person?

Key Takeaways

• GLP-1s are metabolic drugs—not appetite suppressants.
  Their power comes from hormonal effects on fat burning, not reduced food intake.
• Calorie restriction still slows metabolism.
  Even on GLP-1s, dieting triggers significant metabolic slowdown.
• Ad-lib eating outperforms dieting in the research.
  Semaglutide users who ate freely did not show the extra metabolic slowdown seen in dieters.
• Mechanical eating is the most durable long-term approach.
  Regular meals and snacks protect lean mass and prevent famine signaling.
• Mindset shapes hormones.
  Believing a food is “diet” vs. “indulgent” alters ghrelin and satisfaction.
• Track body composition—not just the scale.
  DEXA scans show whether you’re losing fat, muscle, or bone.

Dr. Cooper’s Actionable Tips

• Don’t diet on GLP-1s. Focus on fueling, not restriction.
• Use mechanical eating: predictable meals and snacks, no long gaps.
• Prioritize satisfaction: diet foods often backfire hormonally.
• Follow your real-world data: long-term changes matter more than short-term scale shifts.
• Ask about body composition testing if possible.

Notable Quote:

“What that study proved is that doing the calorie restriction is causing the metabolic slowing… and that’s why it’s so confusing to me that we keep advising people to restrict calories when they’re trying to improve their metabolic function.” —Dr. Emily Cooper

Links & Resources

Podcast Home: https://fatsciencepodcast.com/
Episode References: https://fatsciencepodcast.com/wp-content/uploads/2025/06/Scientific-References-Fat-Science-Episodes.pdf
Cooper Center: https://coopermetabolic.com/podcast/
Resources from Dr. Cooper: https://coopermetabolic.com/resources/
Submit a Question: questions@fatsciencepodcast.com
Dr. Cooper Email: dr.c@fatsciencepodcast.com

Fat Science: No diets, no agendas—just science that makes you feel better. This podcast is for informational only, and is not intended to be medical advice.

This week on Fat Science, Dr. Emily Cooper, Mark Wright, and Andrea Taylor tackle a wide-ranging mailbag episode with listener questions from the U.S., UK, and Europe. Topics include unexpected weight regain on GLP-1s, post-meal sleepiness and hypoglycemia, metabolic dysfunction despite normal labs, GLP-1 dosing strategies, and why these medications are about metabolism, not appetite suppression.

Key Questions Answered

• Why can weight regain happen on GLP-1s even when habits haven’t changed?
• How do leptin, ghrelin, injury, stress, and under-fueling affect weight regulation?
• What does it mean if you get extremely sleepy after meals—is it hypoglycemia?
• Do GLP-1s increase insulin in a harmful way for non-diabetics?
• Can you have metabolic dysfunction with normal A1C, cholesterol, and blood pressure?
• Do GLP-1 medications “wear off,” and how should dosing be adjusted long term?
• Are GLP-1s just appetite suppressants—or true metabolic treatment?
• Is it possible to undo decades of calorie counting and restriction-based thinking?
• What are the risks of the return to extreme thinness in celebrity culture?

Key Takeaways

• Calories don’t explain metabolism. GLP-1 and GIP work across the brain and body—repairing signaling, not just reducing appetite.
• Leptin matters after dieting. Years of restriction and weight cycling can weaken leptin signaling, making the brain defend weight gain.
• Fueling is foundational. Medication can’t replace adequate food, sleep, and recovery.
• Post-meal fatigue is a clue. Reactive hypoglycemia is common and often misunderstood.
• Lowest effective dose wins. GLP-1 success is about pacing, not racing to the max dose.
• Chasing the “last 10 pounds” can backfire. Cosmetic restriction can create new metabolic problems.

Dr. Cooper’s Actionable Tips

• If weight gain appears after injury or stress, focus first on sleep, regular meals, and full fueling, not restriction.
• Suspected hypoglycemia? Ask about a mixed meal tolerance test to assess glucose and insulin response.
• Stay on the lowest GLP-1 dose that’s working and adjust only when progress truly stalls.
• Push back on “appetite suppressant” language—these meds amplify hormones your body already makes.

Notable Quote

“GLP-1s aren’t about eating less—they’re about strengthening metabolic signaling” — Dr. Emily Cooper

Links & Resources

Podcast Home: Fat Science Podcast Website – https://fatsciencepodcast.com/

Podcast Episode References: https://fatsciencepodcast.com/wp-content/uploads/2025/06/Scientific-References-Fat-Science-Episodes.pdfCooper Center for Metabolism & Fat Science Episodes: https://coopermetabolic.com/podcast/
Resources from Dr. Cooper: https://coopermetabolic.com/resources/
Submit a Show Question: questions@fatsciencepodcast.com
Dr. Cooper direct show email: dr.c@fatsciencepodcast.com

Fat Science breaks diet myths and advances the science of real metabolic health. No diets, no agendas—just science that makes you feel better. This show is informational only and does not constitute medical advice.