I was explaining this to my daughter in quite simplified terms the other day- we evolved to taste sugar and enjoy it because finding a sweet edible plant meant we had a source of energy to help us hunt that day. Pretty useful if you’re a hunter-gatherer.
So we seek out sugar. Now we can get it whenever we want it, in much more massive quantities than we are supposed to be processing. Most of us are addicted. I’m not an exception.
The intrinsic sugar in fresh berries with fiber are different than free sugars. Excess sugar is problematic for several reasons, chiefly chronic metabolic and cardiovascular diseases [1]. The more well known among them is insulin resistance. Insulin is an essential hormone for metabolism; without insulin you die (as in the case of type 1 diabetes). The pancreas pumps insulin to get the cells to absorb blood sugar, but if cells don’t respond to the insulin properly (“resistant”), the pancreas keep pumping insulin and eventually cannot keep up resulting in high blood sugar that damages your body [2]. That’s why one should avoid spiking blood sugar. Like many physiological systems sugar triggers a homeostatic response, so the body “expects” a level of sugar consumption once it gets used to it. This is also why artificial sweeteners are problematic: they don’t reduce the dependency on sugar and moreover they disrupt the blood-sugar response whereby you don’t get the same satiety from carbohydrates, etc. [3]. But it’s not all doom and gloom, exercise increases your insulin sensitivity and reducing your sugar intake will almost always result in weight loss [2]. Reducing sugar intake also reduces your sugar dependency but can take a few months.