What is the best way to lower both sugar intake and carbs?

Were you specifically asked to lower sugar and carbs?

Lowering carbs before surgery is a highly preferred method because of the rapidity in fat reduction. Reduces liver size from the very get go which if it's bariatric surgery it's vital considering the liver sits basically over the stomach which makes the surgery more difficult and complicated and it also helps stabilize blood sugars and increases insulin sensitively ultimately reducing infections and improving the healing process and it reduces chronic inflammation which is also vital for recovery. Low carb is based on the success rate in losing weight and patient recovery. Joint replacement another big surgery where people are required to reduce weight is basically for similar reasons and of course less strain from weight on the joints themselves. those are the 2 biggies.

Anyway, the obvious answer would be to consume fewer carbs, especially highly processed carbs considering that's where we find not only the most carbs on a calorie for calorie basis but it's where we'll find the most sugars in it's many forms, and there's a lot of them. The US for example consume about 60% of their food from "ultra processed food" with around 90% coming from added sugars and about another 20% from processed foods so it's a no brainer to remove as much UPF and processed food as we can.

I suspect you are required to lose weight before surgery can be preformed which has to do with not only less risk for you but less risk for doctors as well. They are responsible for "standard of care" which basically comes down to precautions that result in better surgical outcomes which can, if not abided for properly lead down the road to litigation and law suits, so they need to cover their butts as well.

Anyway, the best way to comply to the request of lowering carbs would be to replace those calories with more protein and more fat, but considering obese people have probably 200,000 to 300,000 thousand calories of stored energy that can be utilized I would suggest that you concentrate on more protein and in my opinion from lean animal sources and low carb plant material and if they didn't assign a nutritional expert I suggest you seek out a dietitian that is familiar with low carb and focuses on metabolic health, otherwise you just might get one that says you die of a heart attach if you do low carb, just kidding, but not really.

Adherence is a major problem. Most people are so "addicted" to carbs they simply can't do it and give up, some in the same day but generally within a few days and the big excuse is why should they, so your going to have to try to overcome some pretty intense withdrawal symptoms for the first week or so, but after that it gets much much easier. Good luck in trying to reduce carbs and of course your surgical outcome.