#01 What Are Peptides?

Everyone is suddenly on GLP-1s. Almost nobody is taking them correctly.

In the first episode of Longevity University, Dr. Rehan Muttalib, a Southern California primary care physician who prescribes these medications daily, sits down with XYRx President Milan Costich to break down what peptides actually are, how GLP-1s like semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro, Zepbound) really work, and why he disagrees with the dosing protocols the pharmaceutical companies taught doctors to follow.

Dr. Rehan shares real stories from his practice: the patient whose entire life transformed when the "food noise" finally went quiet, and the cautionary tale of a patient who maxed out her dose too fast and stalled. He lays out his lowest-effective-dose philosophy, the safe rate of weight loss, how to come off these medications without rebound weight gain, and the emerging off-label uses for inflammation, autoimmune conditions, and longevity, including microdosing.

In this Episode: What a peptide actually is (and why insulin was the first) • Semaglutide vs. tirzepatide: why the GIP component may be the difference maker • "Food noise" and why quieting it changes behavior, not just appetite • The dosing protocol Dr. Rehan uses instead of the pharma playbook • How fast you should actually lose weight, and the risks of going faster • Muscle loss, bone loss, and nutritional deficits: the tradeoffs nobody mentions • Diet, protein targets, and resistance training while on a GLP-1 • Could peptides replace steroids? A preview of what's coming

0:00 Cold open: "I've never seen a patient transform like this"

0:24 Welcome from Dr. Rehan (and a quick disclaimer)

1:15 Meet the hosts: how BJJ started all of this

1:54 "Everyone at this dinner was on peptides"

3:20 Insulin: the first peptide

5:04 What is a peptide, actually?

6:18 How GLP-1s work: semaglutide vs. tirzepatide

9:04 The patient story: what happens when the food noise stops

12:14 From diabetes drug to weight loss breakthrough

13:48 This episode is brought to you by XYRx

14:22 Why Dr. Rehan disagrees with pharma's dosing protocols

16:05 The safe rate: 2 to 4 pounds per month

17:23 Milan lost 50 lbs in 3 months. Here's what fast loss costs you

19:59 Dosing by patient type + benefits beyond weight loss

22:21 The ideal protocol: start low, go slow

24:54 Maxed out on the dose and still stalled?

28:03 Switching from semaglutide to tirzepatide

29:07 Coming off GLP-1s the right way

33:34 Diet on a GLP-1: the only rule that matters

37:41 Training and protein: how to keep your muscle

40:19 Building muscle without steroids: peptide stacks

42:56 Dr. Rehan's verdict + what's next

Every week, Physician Dr. Rehan Muttalib and XYRx founder Milan Costich on the real science of male longevity: peptides, GLP-1s, training, and recovery.