I think I've posted this before: the load you can carry doesn't depend on your current weight, it depends on your "normal" (formerly "ideal" but that probably comes too close to body-shaming) weight:

Pack weight is simply a way to quantify pain – but carrying a load doesn’t have to be painful if you limit yourself to what you can comfortably carry. Most people can carry a fourth of their “normal” body weight comfortably. You can find charts that classify your weight as “normal” or “overweight” on the Center for Disease Control website (www.cdc.gov) by searching “Body Mass Index” (BMI.) Your real load includes your gear, supplies, and excess body weight. For example, if your BMI normal weight is one-hundred-eighty pounds, you shouldn’t carry more than forty-five pounds. If you’re ten pounds overweight, your pack shouldn’t weigh more than thirty-five pounds.

It makes sense: I'm about 10 pounds over my "normal" weight, and am not in the greatest shape. At 180, does it make sense that I can comfortably carry a pack that weighs 5 pounds more than a physically-fit 160-pound person? Of course not.