Both MREs and the Mainstay, etc., survival rations are pretty hefty. The latter are highly concentrated and quite dense.

I have a 3-day ration "bar" (it's actually the size of a large paperback book) in the car bag, and I notice the weight. That's why it's in the car bag. The larger emergency backpack (I guess you could call it a BOB) has two of the same bars in it, as well as several packets of instant soup, ramen noodles, tea bags, and some hard candies. It contains a Swedish surplus mess set, an esbit stove and a dozen tabs.

For day hikes I carry a power bar or two, a packet of instant soup and a couple of teabags in case I get lost, break a leg, etc. I carry a stainless cup on my nalgene bottle, but don't take a stove. Materials to make a fire for cooking are readily at hand wherever I hike.