Hey man, want to give you a different angle than the rest of the thread because I think the question you're asking is downstream of a question you should be asking first.
You said your goal is "lose visceral fat while building muscle" and you've "already noticed muscle loss." Tanman's reply was actually solid read it again carefully because he's pointing at the real answer. But I want to add something the thread is dancing around:
You're trying to solve a nutrition and training problem with more drugs. This pattern catches a lot of guys and it doesn't work the way they hope it will. Adding reta, tesamorelin, ipamorelin, GH, more compounds none of these fix the underlying issue if you don't have the fundamentals dialed.
The honest framing:
If you're losing muscle on test alone, something is wrong with your nutrition or training, not your hormones. Test at any reasonable dose should protect muscle in a moderate deficit. If you're losing muscle while on test, one of these is happening:

You're in too aggressive of a deficit. Losing weight faster than ~0.7-1% of bodyweight per week tips into muscle loss territory. If you don't know what your actual maintenance calories are, you can't know if your deficit is appropriate.
Your protein intake is too low. Minimum 0.8g per pound of bodyweight (1.8g/kg) for muscle retention in a deficit. Higher (1g/lb, 2.2g/kg) is better. Most guys who say "I lost muscle" weren't tracking protein and were probably under-eating it.
Your training isn't providing enough stimulus to maintain muscle. Heavy compound lifts 3-5x/week with progressive overload signals the body to retain muscle in a deficit. Doing cardio without resistance training, or training without intensity, doesn't.
You're confusing muscle loss with water/glycogen loss. A scale weight drop in the first 2 weeks of any cut is mostly water and glycogen, not muscle. If you've been "cutting" for less than a month, you probably haven't actually lost meaningful muscle yet.

Why adding reta doesn't fix this:
Reta suppresses appetite. If your problem is "I'm eating in a deficit but losing muscle," reducing your appetite further makes the problem worse, not better. Reta is the right tool when the problem is "I can't stick to a deficit because I'm too hungry." It's the wrong tool when the problem is "I don't understand how much I should be eating."
The other guys in the thread suggesting tesamorelin and ipamorelin are adding complexity to a foundation that isn't built yet. GH/peptides for visceral fat work, but they work best in someone who already has nutrition and training dialed. Throwing them on top of a confused protocol means you won't be able to tell what's working, what isn't, or how to adjust when something goes wrong.
What I'd actually suggest:
Before adding reta or anything else:

For 2-3 weeks, eat at maintenance and just track everything. Use MacroFactor, MyFitnessPal, Cronometer, whatever track every gram of food. The goal isn't to lose weight in this period, it's to learn what your actual maintenance calories are and what your current diet looks like in numbers.
Calculate your protein intake from that data. If you're under 1g per pound bodyweight, that's likely a major contributor to muscle loss before anything hormonal.
Audit your training. Are you actually progressing in your main lifts week to week? Or are you doing the same workout indefinitely? Without progressive overload, you're not giving your body a reason to keep muscle.
Then decide what intervention you actually need. If your maintenance is 2800 cal and you've been eating 1800 cal trying to "cut," your problem isn't appetite, it's that you're starving yourself. Reta would make this worse. If you're eating 3000 cal and can't stop snacking on junk, reta makes sense as a tool to manage that specific problem.

On Tanman's reply specifically:
He laid out exactly the right framework he went from 310 to 230 over a year by figuring out his actual maintenance, using reta as a tool not a crutch, then transitioning to muscle gain at the new maintenance. That's the model that works. Notice he didn't say "add more compounds," he said "do the work properly with the tool helping."
The bottom line that no one wants to hear:
The drugs work best when you're using them to amplify a foundation that already exists. Test, reta, GH, peptides these are amplifiers. If your nutrition and training aren't dialed, you're amplifying nothing. The guys getting impressive results with cycle + reta + GH stacks are guys who already had nutrition and training figured out. Without that foundation, you're paying for compounds, side effects, and risk without the corresponding benefit.
This isn't a lecture about whether you should be on cycle you're already on test, that's your call. But adding more compounds when you don't yet know your maintenance calories is the wrong sequence. Do the boring work first. The compounds work better when they have something to work with.
Tanman's framework is the answer. Spend 6-8 weeks doing the nutrition tracking, dial in training, then decide if reta still makes sense for your specific situation. Most likely it will, but you'll be using it correctly instead of as a panic response to muscle loss that probably has a different cause.

That's going to come down to a calorie thing brother. The people who lose muscle on GLPs, any of them not just reta, use them like a blunt force trauma weapon to crush their appetite and basically starve themselves. Great for them, most people who use them just want to loose weight, they don'tcare where they lose it from. I'm currently on 1.5mg PW, it's just enough to keep the cravings to eat bullshit food away so my diet adherence is great, but doesn't stop me from eating 3300 cals a day without any issues.

I hit my goal weight of 230 in February, started the year 2025 at 310. If you're serious about losing weight while maintaining/ maybe building a little muscle while you're my recommendation would be to take about 6-8 week, count every fucking gram of food you eat every single day, watch what the scale does while you do it, and figure out your TRUE maintenance calories are just to maintain your current weight. From there adjust up or down based on how aggressive you want to lose or gain. This was life changing once I figured it out.

Take the time to lose the weight properly, holding on to the muscle you have, then focus on building it once you reach your weight goal. Once I hit my goal I slowly started increasing my calories until the weight loss stopped, my new maintenance settled in right at 3300 cale a day, THEN my muscle gain went through the fucking roof. From February to today I haven't gained a single fucking pound, sitting comfortably everyday between 230-235, but i was in a calorie deficit for a whole damn year, so just being at maintenance after that has allowed me to put on a ridiculous amount of muscle and strength since then.

Anyway, sorry for rambling, full of caffeine before my morning workout. Don't use reta as a blunt force weapon, use it like a scalpel to HELP your reach your goal, still gotta put in the fucking work though.

Well what’s your overall goal?

Reta is extremely helpful in a cut it gets rid of the food noise and slows down digestion so you feel full quick. But it can also be used to help burn fat while ina lean bulk as well but you have to really plan out your meals. I set alarms to remind me to eat and sometimes i have to force myself to eat.