Energy levels can be greatly affected by hormones and/or depression, which can be issues for people of any size.
I’m fat and have always been fat so my energy levels don’t seem to correlate with my size. It’s not like one time I was thin and then got fat and had an extra “bag of potatoes or two” around my waist. I always played sports throughout school.
No doubt it would be easier to expel my energy if I weren’t so extremely large, but when my depression is in check I get out and do a ton more than, say, my normal-sized SIL.
Certainly fat people have much more energy in the form of fat stored in their bodies. Fat people also have higher metabolisms as they need to burn more energy to move a heavier body. On the other hand, thin people don’t get tired as quickly when they move, don’t get as hot and don’t sweat as much, so I would think they’re more likely to be active than fat people.
Watch the British show “supersize vs superskinny” on Youtube. A fat and a thin person have to eat each other’s diet for a few days and then hopefully both start eating better. Very often, the thin one says they have so much more energy now they’re eating more.
NEAT (Non-Exercise Activity Thermogenesis) plays a role in fat loss. So-called naturally thin people probably have higher rates of movement rather than higher metabolism.
Your blood pumping through the heart comes to mind.
A heart has to work harder in an overweight person so when the over weight person tries to exercise it becomes a real chore for the heart to lift all of that extra weight for longer than it thinks is necessary.
The body talks to us through the heart … “sit down and rest now” is not a voice, but is an urge of your heart to rest.
Skinny people are more efficient and the heart will complain less, but if you strap on a fifty pound back pack … wowie your going to hear some groaning lol
Everyone is a thin person. There’s very little adaptation that the body makes to support being overweight, so for all intents and purposes, we have the same skeleton, the same musculature, the same heart, etc.
Someone who is overweight is, from the standpoint of this question, just the same as a thin person with tens or hundreds of pounds of lard packed into plastic bags and duct taped haphazardly around the body. You’ll grow some extra muscle to deal with it, but it’s certainly not going to make you more spry.