Whenever you have more than 12 to 20 grams of carbohydrates in your diet, insulin is going to be an issue and be raised.
Insulin explained:
Normally, insulin is a good thing. Insulin, after all, is the hormone that unlocks your body's cells so it lets in the sugar in your bloodstream. Once your cells absorbs the sugar, it then converts it into energy. Well, here's the problem with insulin. It has a dark side. When insulin is in your system, your body uses blood sugar for fuel. This means it's not burning fat. In fact, insulin has the effect of locking your fat cells so none of that energy gets out. Your body is blocked from using fat as energy. That spare tire you're walking around with will remain with you until and unless you deal with insulin. Reduce insulin and your body starts burning fat for fuel. It's that simple.
The problem is the 'standard American diet' (SAD) has so much carbohydrates that people starts suffering from the excesses of insulin. Not only do they have spikes in insulin levels which leads to them feeling hungry throughout the day, a high-carb diet also inflames your system.
Ketosis works because 'ketones' themselves are only present when insulin is not elevated, which means the body is burning fat as fuel. No ketones, not fat-loss.