There is a concept called "base weight". It addresses all the weight you will be carrying that will not be consumed during your hike. Food, water, and fuel are not part of base weight, but it describes your clothing, shelter, backpack and other durable items. There may be some days when you may need to carry quite a bit of food, water and fuel, so that your entire pack weight might conceivably be 45 lbs. But ideally that weight will largely disappear in a relatively short time.

I would aim for a base weight in the range of 20 lbs or less. Most of the hikers here will carry a base weight less than that, even for short backpacks. My base weight is roughly 15 lbs. If you can meet a base weight below 20 lbs, by all means do so. In order to thru-hike the AT you will need to walk high miles when you're on the trail to make up for all the days when you must leave the trail for resupply, repair, and rest.

Carrying just one extra pound for 2100 miles puts an extra work load on your muscles and joints. The further you hike on the AT the more you will physically appreciate the 'weight' of this fact. Every thru-hiker learns this lesson and the sooner it sinks in, the better off you'll be.