This is so biologically illiterate, I genuinely don't know where to start.
Firstly, nobody is claiming our bodies can just "adjust" to a diet much higher in sugar than is natural. The over-abundance of various sugars in our diet is a contributor to the obesity crisis, increased risk of heart disease, etc.
But do you know what actually
causes those cardiovascular issues? Obesity places additional strain on the heart and muscular system, as it must work harder to provide the necessary oxygen to the body; and non-HDL cholesterol builds up in the arteries, narrowing the available space for blood flow, again restricting oxygen provision.
What causes high levels of non-HDL cholesterol? The main contributor is
a diet high in saturated fat. What causes weight gain, leading to obesity? A diet containing significantly more calories than are exerted through exercise... which are then stored as
fat.
And do you know why sugar is identified as a major contributor to the obesity crisis and heart disease? Because if you ingest more than can be stored by your liver and muscles, it converts into....
fat.
It is transferred into fatty acid in a process known as lipogenesis.
(On a side-note, do you think that 200,000 years is in any way significant from an evolutionary standpoint? 200,000 years is fuck all. Even a few million years is very little if we're talking about evolutionary developments. The idea that 200,000 years, or a million, would surely have ironed out any issues we have with our diet shows very little understanding of the timescales involved in evolution. I mean, humans still have an internal organ which is entirely unnecessary to our survival, and yet occasionally ruptures and kills us. Why hasn't evolution ironed it out? Because
that's not how evolution bloody works!! If something is disadvantageous, it can still stick around in a species for millions of years!)