Breakfast in South India begins with piping hot idli and chutney. There are a few reasons for it. In the past many folks got rice let alone idli once a year during the harvest festival of Pongal. That's why in Tamil, "nel soru" was the term for cooked rice. Most ate millets like "kambu soru", "kelvaragu soru" etc., With affordability and government policy, almost all consume rice and rice-based dishes like idli. Next is convenience. Idli batter is prepared ahead of time and kept ready to use at a moment's notice. Idli batter can be bought if you don't want to do any prep work. Idli is made in batches which helps to serve the whole family in a matter of minutes.
The last reason is time constraints. As folks started working in factories and offices, far away from their homes, they had to take their lunch with them. The same way you do for school. So, typically a mother had to cook 2 meals for as many people in the house all in a short span in the morning among other things. No wonder, idli made from white rice became the go-to dish.
If the idli is eaten with sambar, a famous South Indian side dish, it still would be okay. Sambar is versatile and can be eaten with idli or rice. But chutney can only be eaten with idli. So, Sambar is made for lunch. The chutney of choice was coconut chutney. It has fat that provides satiety. But as we got addicted to sugar, tomato and onion chutney has become the de facto standard today. Though no sugar is added to the chutney, it is a dish rich in sugar as tomato is a fruit. Don't let anyone tell you otherwise. Onions are caramelized to bring out the sugar in them.
So, what happens when you eat this breakfast and go to school? You feel very energetic and raring to go for the first two classes or so. It's because the glucose level in your blood is high as shown in the graph below. I don't have a graph for idli and tomato chutney. But we can see what happens when we eat an equivalent breakfast of bread and jam. Bread like idli does not contain any sugar until you toast it. Jam contains sugar just like tomato chutney.
After 2 hours, your blood glucose levels take a dip. This is why you get very hungry before the morning interval and are unable to focus on your studies afterward. Eating fruits, fruit juice, or any carb-rich snacks will only make your blood sugar go up again and crash before lunchtime as seen in the graph below. The same story continues after lunch if you continue to eat a carb-rich lunch like rice and potatoes. I will stick with breakfast for the sake of brevity. But you get the idea.
To escape from this roller coaster ride and be able to focus on your studies throughout the day, you need to find ways to eat that will keep your blood sugar level steady throughout the day. That involves eating fiber, fat, protein, and carbs in that order. You can see in the graph below how eggs and avocados keep our blood sugar steady for 3+ hours.
Not all eat eggs. Fret not, India is a land of diversity in all aspects including food. Paruppu Adai and coconut chutney have fat and protein. If you are from Andhra, pesarattu with peanut chutney will do the trick. If you absolutely love idli, switch out the sugar-rich tomato chutney for fat-rich coconut chutney or groundnut chutney. If you must eat snacks, pick something rich in fat and protein as well like sprouts, cashew nuts, roasted ground nuts, and boiled egg. Now that you know how food affects your blood glucose level, it's up to you as kids to come up with the right combos to suit your palate while keeping your blood sugar steady.
In case you are curious as to how your parents and grandparents who ate idli and tomato chutney survived without any sugary snacks during the morning interval, please read on. They rode their bikes or walked to school. The sugar was used by their muscles by the time they reached school. Since there were no highs there are no dips afterward.