A while ago, a friend questioned why sugar rush is bad and what's wrong with repeated sugar rushes. I'm sad to say that I've been so out of touch with dietary nutrition that it took me quite a while to come up with an answer, and the answer couldn't even fully address why repeated sugar rushes are not recommended. So, after quite a bit of research, this is what I've found.
The basics of the so-called sugar rush is a high consumption of simple carbohydrates (such as white sugar, white bread, candy, sugary drinks, refined sweets, etc) followed by a sudden decrease of the ingested sugar (which becomes glucose) as the body secretes insulin to eliminate the glucose from the bloodstream. The lowered glucose level can then trigger another craving for sugar, which can become a cyclical process. So what's bad about this?
Well, certain sources state that the glucose removed from the bloodstream becomes stored in the fat cells. If we look at the fact sheet from the British Dietetics Association (BDA), it does not state this nor does it link high sugar intake to diabetes. The weight gain is from the types and amounts of food eaten to satisfy the sugar cravings. Most of these foods contain a lot of fat and calories, which leads to consuming too many calories and to weight gain.
There's even one article from the Journal of Community Nursing (???) proposing that the "low" from the sugar rush, called reactive hypoglycemia or postprandial hypoglycemia, is not really hypoglycemia in the clinical sense. Instead, the "low" felt by people may be caused by the low protein and fat intake that is traded-off by the high sugar consumption, or, the increased physical expenditure due to the sugar energy rush.
Of course, this by no means suggest sugar is good for you. The most imminent problem is tooth decay and the potential missing nutrients required by the body. Then, there are the possible links to poor skin conditions. And as with anything, eating out of moderation can lead to weight gain and all the risks associated with the gain. So how much sugar is too much? Well, there is no recommended daily allowance. The standard advice is to consume more complex carbohydrates and keep refined carbohydrates to a minimum. As with everything (nutrition-wise, at least), moderation is key.

