Why do so many Americans gain weight from eating high carb foods like rice, but people in Asian countries can eat it all day and seemingly not gain any weight?

The problem isn’t carbs like rice or flour, the problem is added sugar.

One thing I noticed when I first came to the US is how sweet everything is. And this sentiment is shared by a lot of Chinese. When we first eat muffins, it is so sweet we nearly gagged.

A lot of processed food (even savory snacks) has a lot of sugar in it.

Not to mention soft drinks.

Another thing is for urban Americans, it’s much harder for them to get fresh produces compare to urban Chinese.

For example, I used to live in Beijing. And on my way home there are farmer’s market street stalls selling fresh produces.

This kind of “farmer’s market” is integrated with pretty much all communities. People buy fresh produce on a daily basis and they cook fresh, mostly plant based food instead of relying on boxed meals or heavily processed foods like “hamburger helper”

After I come to the US, the only places I can purchase fresh produce are supermarkets and occasional “farmer’s markets” that only show up on Sundays in selected areas. Fresh produce is often more expensive than processed food.

Comparatively, the fresh produce in these street markets is pretty cheap. If you’re a poor person in China, you’ll most likely maintain a plant-based diet. If you’re a poor person in the US, you are limited to processed food and can food. All of them have added sugar.

For example, this is a regular bento box usually sold for low-income people like migrant workers. This one cost 10 RMB (about 1.75 USD)

Yeah, it doesn’t look good, but 1) they’re freshly made. 2) LOTS of vegetables. 3) looks pretty balanced with veggies and proteins.

So even if you’re poor, you don’t have a place to cook, and had to rely on cheap ready-made food, you still ended up eating pretty healthy.

China had seen a wave of childhood obesity back in the 80s and 90s when Coca-Cola and other western soft drinks and fast-food chains were first introduced to our market.

But Chinese diet somewhat reduced the effect of that, and the fast-food joints in China aren’t cheap. There are other cheaper, healthier street food options. And things started to get better once people (parents) started to realize how soft drinks and fast food is bad for their children.

So at the end of the day, it’s the added sugar and cheap processed food.

As mentioned in a comment, portion control also plays a huge part in the East Asian diet.

For example, this is the bento lunch box sold on Chinese railways

You have a good portion of leafy greens, some protein, and rice (carbs). This is usually enough for an adult male, women and children often eat less.

This is an elementary school lunch:

Pretty healthy and balanced food with some multi-grain, fish protein, vegetables, and fruit.

When my Chinese friends and relatives came to the US, and we have lunch or dinner at an American restaurant, we often warn them about the portion size, ask them to look at other tables and see how big the plates are. Many would choose to share plates. Partly because Chinese are more used to family-style, partly because American restaurant’s portion is ridiculous.

And I think the family-style meals also help with portion control. With family-style, you’re free to eat until you’re full, instead of feeling obligated to finish the food on your plate. Sure, you can keep eating from the plate, but if you’re eating with a family, it’s kind of bad manners to hog on food. So there’s some peer pressure to not overindulge.