Protein and muscle on a GLP-1

Why protein and muscle come up during weight loss

When the body loses weight, what’s lost isn’t always fat alone. A peer-reviewed review in the journal Nutrients describes that consuming higher amounts of protein during a moderate energy deficit can help preserve muscle mass during weight loss.¹ That’s the reason protein keeps coming up in weight-management guidance.

Protein matters beyond weight changes, too. MedlinePlus explains that the body needs protein from the foods we eat to build and maintain bones, muscles, and skin, and that you need to eat protein every day because the body doesn’t store it the way it stores fats or carbohydrates.²

None of this is a personalized target. How much protein a person needs depends on their own situation — MedlinePlus says it depends on age, sex, health, and level of physical activity.² The sections below describe what authorities and dietitians have published, not a plan for any one person.

What authorities and dietitians say about protein amounts

A joint recommendation from the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine sets protein intake at 1.2–2.0 grams per kilogram of body weight per day for physically active people, as summarized in the Nutrients review.¹ That figure is described in the context of activity, not as a one-size-fits-all number.

The same review reports that protein intakes on the order of double the current recommended dietary allowance — about 1.6 g/kg/day — have proved efficacious in preserving muscle mass during weight loss.¹ It frames this as a research finding, not an instruction.

On the everyday side, MedlinePlus distinguishes protein quality: proteins from meat and other animal products are complete proteins (they supply all the amino acids the body can’t make on its own), while most plant proteins are incomplete.² This is general nutrition background, not a directive about what to eat.

Where strength training fits in

Authorities pair protein with movement. The CDC states that muscle-strengthening activities can help you increase or maintain muscle mass and strength, and adds that it’s important for older adults who experience reduced muscle mass and strength with aging.³

On how often, NIDDK suggests aiming for at least 2 days per week of strength-training activities and exercising all the major muscle groups — the legs, hips, chest, back, abdomen, shoulders, and arms.⁴ NIDDK also notes that strength training may help you build and maintain strong muscles as you get older.⁴

The research review ties the two threads together: a meta-analysis it cites found significant positive associations between coupling resistance exercise with post-exercise protein intake and total fat-free mass, strength, and muscle size.¹ As above, this describes findings — not a routine for any individual.

How a companion app fits — and what it can’t do

Tonic is a tracker and companion. It can help you keep a record of what you eat and how you move, and surface the kind of general, source-based information you’re reading here. It doesn’t diagnose, prescribe, or replace your own clinician.

Protein targets and exercise plans are personal — the published numbers above depend on body weight, activity, health, and age, as the sources themselves note.^1,2 A clinician or registered dietitian is the right person to translate any of this into something specific to one body. If you take a GLP-1 medication, your prescribing clinician and care team know your history.