GIP

How GIP Works

GIP is released from K-cells in the upper small intestine:

1. Nutrient sensing - Fats and carbohydrates trigger GIP release
2. Rapid secretion - Released within minutes of eating
3. Pancreatic effects - Enhances glucose-dependent insulin release
4. Metabolic effects - Influences fat storage and bone metabolism

GIP vs GLP-1

Feature	GIP	GLP-1
Source	K-cells (upper gut)	L-cells (lower gut)
Half-life	~5-7 minutes	~1-2 minutes
Gastric emptying	No effect	Slows
Appetite	Minimal effect	Reduces
Fat metabolism	Promotes storage	Promotes oxidation
Glucagon	Context-dependent	Suppresses

GIP and Obesity Paradox

GIP has a complex relationship with obesity:

In Normal Weight

• Enhances insulin secretion effectively
• Contributes to incretin effect
• Normal receptor sensitivity

In Obesity/Type 2 Diabetes

• Reduced insulinotropic effect
• Receptor sensitivity may be impaired
• GIP receptor antagonism was initially studied for weight loss

The Tirzepatide Surprise

• Dual GIP/GLP-1 agonism shows superior efficacy
• GIP agonism contributes to weight loss (contrary to expectations)
• Mechanism still being researched

GIP Receptor Distribution

GIP receptors are found in:

Tissue	Function
Pancreatic β-cells	Insulin secretion
Adipose tissue	Fat metabolism
Bone	Bone formation
Brain	Potentially neuroprotective
Stomach	Gastric acid secretion

Dual and Triple Agonists

Tirzepatide (GIP/GLP-1)

• Activates both incretin receptors
• Superior A1C reduction vs GLP-1 alone
• Greater weight loss vs GLP-1 alone
• FDA-approved for diabetes and obesity

Retatrutide (GIP/GLP-1/Glucagon)

• Triple hormone agonist
• Adds glucagon receptor activity
• In clinical development
• May show even greater weight loss

GIP Research Evolution

Understanding of GIP has evolved:

• 1970s: Discovered, named “gastric inhibitory polypeptide”
• 1980s: Renamed “glucose-dependent insulinotropic polypeptide”
• 2000s: Thought to be less important than GLP-1
• 2020s: Tirzepatide success renewed interest
• Current: Active area of metabolic research

Frequently Asked Questions

Why aren’t there GIP-only medications?

GIP alone doesn’t reduce appetite or slow gastric emptying like GLP-1, so GIP-only drugs would have limited weight loss benefits. The real power seems to be in combining GIP with GLP-1, where they work synergistically.

Does GIP make you gain weight?

This was a concern based on GIP’s role in fat storage. However, clinical trials with tirzepatide (GIP/GLP-1) show significant weight loss. The full picture of GIP’s metabolic effects is more complex than initially thought.

What’s the difference between tirzepatide and semaglutide?

Semaglutide activates only GLP-1 receptors. Tirzepatide activates both GIP and GLP-1 receptors. In head-to-head trials, tirzepatide showed superior glucose control and weight loss, suggesting the dual mechanism provides additional benefits.