Unfortunately, dieting will not change anything unless you really change your lifestyle and eating habits forever.
Any diet is a failure if it's just something you do for some time, just to get back to the old habits once you shaved off some pounds. Because of that, keto diets are not a good solution, since people get the wrong assumption about dieting ("I can eat like an animal and then do some keto to get fit again") and they're very likely to induce some sort of weight cycling (the so called yo-yo effect).
Therefore keto should be used with caution, by people who do that with knowledge and with the help of a professional. Sticking to healthier eating habits over time is much more difficult and you need a very, very strong commitment. At some point in time, though, there's a switch that finally clicks and everything becomes more easy. Exercise should be a big part of this journey.
In the end it's much more rewarding and you'll discover a whole range of benefits. Weight loss will be just an insignificant detail, then.
They aren't? Are there strong hints* that this is true? I didn't see any so far, but that may be due to my limited research.
Carbs in general (ones that metabolize mostly into glucose) have been widely available for a long time. They are also processed in a more "normal" way than fructose.
It might still be a good idea to reduce carbs, but I'm skeptical that the ketogenic diet is healthy.