One number answers this, and it is 1.2 to 2.0 grams per kilogram of body weight per day [2]. At 90 kg that is 108 to 180 grams daily. The source is a 2025 narrative review rather than a guideline, and the range is reproduced here with that attached. No target on this page belongs to this desk.
The rest of the question is arithmetic rather than pharmacology. Protein stays a steady share of what you eat, and you eat considerably less. A steady share of a smaller total is a smaller amount. That is the same accounting problem as reading a lean-mass figure without its comparator. It sits directly underneath how much of the weight comes off as lean mass.
What the trials measured
The review gathers the dietary data from incretin trials. Liraglutide generally maintains protein intake as a proportion of total energy, in the region of 13.9% to 17.5%. [1] That sounds like a reassuring finding and it is the wrong unit for the question being asked.
Those percentages come from liraglutide studies. The authors note the concern grows with more potent appetite suppression. That is where the newer drugs sit, and where the dietary data are thinnest — the same ordering as the gap between the molecules on weight.
How much less you are eating
A separate meta-analysis of 19 incretin trials puts a figure on the total. Daily energy intake fell between 24.0% and 39.2%, depending on the drug [3]. The authors model daily deficits reaching 1,200 kcal, which is an estimate and not a measurement.
Hold the share at 15% and cut the total by a third. The protein falls by a third with it. That is the whole mechanism, and no trial in either paper reports the grams on either side of it.
The same analysis recorded what the shortfall looks like in the blood. Investigators logged malnutrition as an adverse event in 0.12% of participants. Lab screening flagged low lymphocyte counts in 2.90% on active therapy, against 1.77% on placebo — a gap between what was recorded and what was measured.
What the 1.2 to 2.0 figure rests on
A narrative review summarizes a literature and makes suggestions. It does not test the suggestions. The same document names seven other supplement categories alongside the protein target, and the strength of the evidence behind each one differs [2]. Their prices are counted in the shopping list nobody prices.
The protein line is the one with a trial behind it, and the trial is about training rather than powder. Supervised resistance training over more than ten weeks added around 3 kg of lean mass and about 25% more strength [4]. Protein without the training is the half of the recommendation nobody has isolated.
The gap where the outcome should be
Nobody has shown that this causes measurable harm. The review says comprehensive dietary data remain limited. Few studies have tested whether reduced protein intake translates into declines in muscle mass, strength or physical performance.
So what exists is a plausible mechanism and an absence of outcome data. That is not a demonstrated risk. It is not nothing to worry about either. The authors ask for longer trials with dietary assessment, body composition and function measured together. How much of the loss is lean tissue at all is measured drug by drug.
Nobody sells this alongside the drug
No seller tracked here includes dietary assessment, and the coaching products that do exist are sold separately and have been evaluated without randomization.
That is worth knowing before treating a subscription as a weight-management program. What arrives is the drug, and most people are not on it a year later. The window in which any of this matters is usually short. While it is open, nobody is watching what you eat.