The formulas
protein range (g/day) = weight (kg) × 1.2 to 1.6 protein minimum (RDA) = weight (kg) × 0.8 fluids from drinks = 2.2 L (women) or 3.0 L (men) a day
Pounds to kilograms: divide by 2.2046. For example, 180 lb is 81.6 kg, so 1.2 to 1.6 g/kg is 98 to 131 g of protein a day.
Why protein matters during weight loss
When weight comes off, part of it is muscle. Studies of GLP-1 medicines found that lean mass makes up a meaningful share of the weight lost, which is why the joint advisory puts protein and strength training among its priorities. A smaller appetite makes it harder to reach a protein target, so many people find it easier to eat the protein part of a meal first and to spread protein across the day.
How much protein is in common foods
Protein per typical serving, from USDA FoodData Central. Brands and recipes vary, so check the label for packaged foods.
| Food | Serving | Protein |
|---|---|---|
| Egg, large | 1 egg (50 g) | 6.3 g |
| Chicken breast, roasted, skinless | 3 oz (85 g) | 26.4 g |
| Turkey breast, roasted | 3 oz (85 g) | 25.6 g |
| Lean ground beef (90%), cooked | 3 oz (85 g) | 21.4 g |
| Salmon, Atlantic, cooked | 3 oz (85 g) | 18.8 g |
| Shrimp, cooked | 3 oz (85 g) | 20.4 g |
| Greek yogurt, plain, nonfat | 7 oz container (200 g) | 20.4 g |
| Cottage cheese, 2% | 1 cup (226 g) | 23.5 g |
| Milk, 2% | 1 cup (244 g) | 8.1 g |
| Cheddar cheese | 1 oz (28 g) | 6.9 g |
| Tofu, firm | ½ cup (126 g) | 21.8 g |
| Lentils, cooked | 1 cup (198 g) | 17.9 g |
| Black beans, cooked | 1 cup (172 g) | 15.2 g |
| Peanut butter | 2 tbsp (32 g) | 7.1 g |
| Almonds | 1 oz, about 23 nuts (28 g) | 6.0 g |
| Oats, dry | ½ cup (40 g) | 5.3 g |
Putting it together: 2 eggs (12.6 g), a 7 oz Greek yogurt (20.4 g), 3 oz chicken breast (26.4 g), 1 cup of black beans (15.2 g), 3 oz salmon (18.8 g) and a cup of 2% milk (8.1 g) add up to about 101 g. This is an example of how servings add up, not a meal plan.
Fluids
The National Academies didn't set a strict water requirement. They set an adequate intake from what healthy adults actually drink: about 3.0 liters of drinks a day for men and 2.2 for women, plus water from food. Plain water, milk, tea, coffee and soups all count. Needs go up in heat, with exercise and with fluid loss from vomiting or diarrhea.
Questions
How much protein do I need on a GLP-1 medicine?
The 2025 joint advisory from four obesity and nutrition societies notes that the general adult minimum is 0.8 g per kg of body weight a day, and that higher targets of 1.2 to 1.6 g/kg have been proposed during active weight loss to help keep muscle. Your prescriber or a dietitian can set a number for you, especially if you have kidney disease.
Why is there no automatic adjusted-weight target?
The 2025 advisory says it is unclear whether protein goals in people with obesity should use actual weight, adjusted or ideal weight, or fat-free mass. This calculator displays actual-weight arithmetic and flags that uncertainty rather than selecting a correction formula. A dietitian can choose an appropriate target.
How much is 100 grams of protein in food?
By USDA figures: 3 oz of roasted chicken breast has about 26 g, a 7 oz container of plain nonfat Greek yogurt about 20 g, two large eggs about 13 g and a cup of cooked lentils about 18 g. The table on this page lists more foods; labels give the grams for packaged foods.
Is the half-your-body-weight-in-ounces water rule right?
It isn't from any official source. The National Academies set an adequate intake by sex, not weight: about 2.7 liters of total water a day for women and 3.7 for men, with roughly 80% coming from drinks. The calculator shows the drinks part.
Do I need more water on a GLP-1 medicine?
The medicines can cut thirst along with appetite, and nausea, vomiting or diarrhea lose fluid. Dark urine, dizziness and headaches can be signs of dehydration. Tell your prescriber if vomiting or diarrhea keeps you from holding fluids down.