Why protein needs increase during weight loss
When you eat in a calorie deficit, your body is short on fuel — and without enough protein, some of the weight you lose comes from muscle, not just fat. Eating more protein relative to your total calories helps signal to your body to preserve muscle tissue while it draws energy from fat stores instead. This is why this calculator uses a higher protein-per-kg figure for a weight-loss goal than it does for simple weight maintenance.
Protein also helps with the hardest part of dieting
Protein is the most filling macronutrient gram-for-gram, which matters most when you're eating less overall. Meals built around a solid protein source tend to keep hunger down for longer than the same number of calories from carbs or fat alone — which is a big part of why high-protein diets are easier to stick to than low-protein ones at the same calorie level.
How your weight-loss target is calculated here
If you enter a goal weight below your current weight, this calculator doesn't simply use your current weight or jump straight to your goal weight — it moves your reference weight partway toward your goal, scaled to how much you have to lose. Someone with a small amount to lose sees almost no change; someone with a lot to lose has their target calculated closer to the body they're working toward, since carrying a lot of excess fat doesn't raise protein needs the way carrying more muscle does.
What to eat to hit a higher protein target on fewer calories
Lean, low-fat protein sources let you hit a higher gram target without blowing your calorie budget — think chicken breast, white fish, egg whites, non-fat Greek yoghurt and lean beef mince. See our protein foods guide for protein-per-calorie comparisons, or browse high-protein meal ideas built for exactly this.
On a GLP-1-based medicine?
If you're eating much less than usual on a prescribed GLP-1-based medicine, published guidance uses different protein ranges. See our GLP-1 protein calculator and guide to protein and GLP-1, and check with your healthcare team.
FAQs
Do I need more protein when losing weight?
Yes — protein needs go up, not down, during a calorie deficit. It helps preserve muscle mass and keeps you feeling fuller on fewer calories, both of which matter more while dieting than while maintaining weight.
Will eating more protein help me lose fat faster?
Protein itself doesn't burn fat, but hitting a higher protein target makes it easier to stay in a calorie deficit consistently (through better fullness) and helps ensure more of the weight you lose is fat rather than muscle — both of which support better results over time.
Should I use my current weight or goal weight in the calculator?
Enter both if you have a specific goal weight — the calculator blends the two rather than using either one alone, weighted by how much you have to lose.