I am confused as to why the human body has so many regulation mechanisms, yet seems to fail many of us in excess weight gain. Why can’t the body just increase the metabolism/heart rate in overweight people, to help burn off the extra calories?
In: Biology
Because we evolved in a world where famine was much more common than surplus. As a hunter/gatherer we had to make good use if every calorie. There hasn’t been time or enough of a issue to make it change.
Humans have evolved with very little fat/salt/sugar. That’s why we like those kinds of foods so much and why our bodies are really good at storing fat. It’s like your body is thinking “well it’s going to be a *long* time before I see this again, might as well hold onto it” even though we have food in excess now.
We do have regulatory mechanisms that help us keep at a normal weight actually. The metabolism does go up when you eat more, the hormone responses make you not feel hungry anymore, you get an uncomfortable feeling when being too full, you get a burst of energy that allows you to burn more. The body doesn’t really like change, so it’s trying to maintain always. If you are metabolically healthy it will be actually hard to gain weight at the very beginning of your overeating.
The thing is that with the processed diet that most of us have and the lifestyle we lead if you will usually get hormonal imbalances before you even get obese. Processed food is actually designed to make you crave it more, even if you are full. And then it’s a cycle it’s hard to get away from.
Our bodies can only use so much energy depending on level of activity. It has to do with the amount of calories consumed vs used. The less active you are, the less calories your body needs to function properly. If you consume enough for a more active lifestyle and remain inactive your body will store it as fat, thus gain weight.
For the same reason that you can’t just overclock a computer as hard as you want: **all** energy eventually ends up as heat. Those calories have to go *somewhere*. To reach a healthy weight, you need to exercise, burning off the energy as the movement of muscles. This still generates waste heat and if you’re doing it in a hot environment your body can’t shed the heat fast enough and you suffer from heat exhaustion or heat stroke.
If your body isn’t doing *anything* except sitting around, what are those calories doing? They’re just producing heat that isn’t going anywhere. To make it worse, fat is a good insulator, *and* larger bodies have a more difficult time shedding heat. Just increasing a person’s metabolism means increasing the amount of heat their body is generating, which will strain the body’s ability to remove that heat.
Regardless, this isn’t a problem of whether or not such a mechanism *can* exist, the problem is that it *doesn’t*. Excess calories is a distinctly modern problem. For millions of years of evolution, calories are hard to get. Organisms have to claw and fight and search and hunt and out-compete everything around them trying to use the same source of calories. Meals are not guaranteed. No creature spends calories unnecessarily.
Humans, like all living things, are built to horde precious calories to get through leaner times. The problem is that human biology is used to getting maybe a few extra calories at most, which might last for several days if the body takes extreme measures to survive. Having access to, much less consuming several thousand extra calories daily is something that arose only in the last few thousand years as humans invented agriculture, and even then calories were still relatively uncertain. Today, you can get multiple days’ worth of calories in a single meal, and our biology simply hasn’t had enough time to evolve ways to deal with that.
Latest Answers