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Eating vs. drinking calories on GLP’s

12 replies9 peopleOct 12, 2026☆ Follow
Summary

Is it okay to rely on protein shakes and liquid calories to hit macros while using GLP-1 medications instead of eating mostly solid food?

Users on Retatrutide or Tirzepatide report that the usual reasons to prefer solid food over shakes no longer apply because the drugs already provide strong satiety. Several people are successfully using shakes for one or two meals plus one solid meal, adding fiber supplements, and still progressing with training. Concerns raised include possible micronutrient shortfalls and stomach tolerance to high whey intake, with advice to get bloodwork and treat the approach as temporary. Overall the group sees no inherent problem as long as macros, fiber, and micros are covered.

What this discussion establishesWhere people disagree

Whether a mostly liquid diet risks missing important micronutrients even when macros are met

Still open

Long-term effects on digestion, nutrient status, or body composition once users reach maintenance or stop the medication

Nothing here is advice.

12 replies · 9 people
RustTimber42archiveopening post11h

I’ve spent nearly twenty years around fitness and the usual advice for both bulking and cutting has always been to eat your calories rather than rely on shakes or smoothies. After a month on Reta where I stay full and can hit my numbers more easily with liquids, I looked into the science. The two main arguments for solid food, satiety from chewing and slower digestion that triggers GLP-1 and PYY, are already handled by the medication itself, so a protein shake can leave me satisfied while letting me reach my targets better than struggling with a partial solid meal.

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BlueSignal49archive11h

GLPs probably remove the need for any special diet rules. Just eat normally. When people warn about liquid calories they usually mean soda and juice, not a protein shake.

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GreyLantern71archive11h

Not using Reta, but the effect might depend on dose. My carb tolerance improved only after the third 7.5 mg shot of Tirz.

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RustTimber42archive11h
↳ replying to @BlueSignal49

In my case two meals a day come from protein and fiber shakes and lunch is solid food with lots of vegetables plus fish or similar protein. The fitness crowd would probably call that a bad idea because they want calories from whole food, yet the reasons behind that rule seem irrelevant once Reta is in the picture. I’m not talking about juice cleanses or fad liquid diets.

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RustTimber42archive11h
↳ replying to @GreyLantern71

Carbs sit fine with me so far at just 1 mg every five days. Five weeks in the appetite control is still steady. I’m eating 120-150 g of carbs daily and the only change is a small drop in morning lifting stamina.

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AmberBeacon57archive11h

The strongest case for whole food might be the extra micronutrients and trace compounds in meat and plants that powders lack. Could you combine both, keep small solid meals and use a shake as a treat to close the gap on your targets?

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AmberMeadow80archive11h

While dropping weight I aimed for 1800 calories and 100 g protein. Some days the only way to reach the protein number was a scoop of powder, and occasionally a protein bar at the end of the day. In maintenance I’ve shifted back to mostly real food and stopped tracking.

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RustTimber42archive10h
↳ replying to @AmberBeacon57

I already said that in the first post and I’m already mixing both, though I may still need an extra shake some days to reach protein.

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SharpMarble40archive6h

Same situation here, shakes plus one solid meal make hitting protein and calories much simpler. I add fiber too. A diet that is 60-70 % liquid does not seem to hurt fat loss or muscle gain on reta if it stays protein-focused and training continues. I see it as a short-term phase and plan to move back to mostly solid food near maintenance. My stomach can get unhappy with all the whey though.

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PatientWillow17archive4h

That is a big share of the diet from liquids, but if macros stay balanced and you keep fiber and micros adequate then go for it. When solid food is hard to get down in enough volume, a shake or smoothie can be the difference between falling short and meeting needs. Even if solid food is ideal, don’t discard something useful while chasing perfection.

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RustTimber42archive4h

Quick math showed I used to drink 4000-5000 calories a week in beer last year. Not doing that again.

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LevelThistle44archive4h
↳ replying to @RustTimber42 (opening post)

I don’t see a problem. Some days almost everything I eat is liquid. I would run bloodwork to watch for micronutrient gaps. My lipids look good but fatty acid balance is a bit off and B6 came back low, so I added a multi and fish oil and will retest later.

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IronLantern24archive3h

Without shakes I would never get near the protein intake I'm trying to achieve.

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