As an older (think 60s) hiker, my first thought is packing to avoid injury, in my case, knee injury. Too much weight is going to aggravate old injuries or create new ones. I have seen first hand what happens when someone packs too heavy and damages their knees; and this is when we were 17 years old. Evacuating my friend from Camels Hump in Vermont was not a great experience; but it is memorable😀.
So after 45+ years of hiking, here are some of the things that I focus on when it comes to weight and protecting my body.
1) My own personal health and BMI. For every pound of unnecessary weight on my body, is a pound that is not in pack. If I am planning a longer hike, shedding winter weight is my first priority.
2) Hiking with a friend/partner. This allows us to distribute the weight of stoves, cookwear, first aid kits and other common items.
3) Hike in areas with shelters. Carrying a tent is extra weight that can often be avoided. In the summer, thunderstorms require shelter that a tent cannot provide; another rational to skipping the tent.
4) if possible, check your weather window for your hike. There is no value bringing a lot of extra clothes that will not be needed. Weather forecasting is pretty good at the big picture on a 7 day time frame; they might be off on timing, but if it is forecasted to be cold and wet, it is likely to be cold and wet.
5) Know how much weight your body can take before you hit the trail with a heavy pack. Do smaller hikes and keep track of the pack weight and any resulting aches and pains. Learn your body's weak points, be they your back, knees or heart. Depending upon family history, it may be prudent to have a cardiac stress test done to understand how much pressure you can put on your heart. As weight is added to your body via a backpack, the HR increases as does blood pressure. Knowing how your body reacts to heavy exercise loads can help you make better "packing" decisions. Younger people can justify a stress test by choosing a VO2 Max test (if performed by a competent person).
6) Make sure your footwear can handle the extra weight you are carrying. A hiking shoe that does great on a day hike is not likely to handle a 45 pound pack.
7) Trekking poles can be useful to engage your arms to support some of the weight. The latest carbon models are so light, they are easily justified.
Like everything else, experience is the best teacher. The more hikes you take, the more you can learn about how your body responds to the stresses of hiking, climbing, hiking food and water.