The key driver of modern obesity is the high availability of varied and intensely pleasing flavors. Even thirty years ago food was more bland, and there was way less variety in the grocery store. 100 years ago cooking with spices was a rare treat. Animals get fat on what is called the "cafeteria" diet, where they are presented with the choice of a high variety of flavors and nutrients. They do not get fat when presented with a monotonous diet.
Low carb dieting works because you are reducing food reward by removing pleasant starchy and sweet flavors, so people eat less. Low fat dieting also works for the same reason; people have had success by eating mostly plain potato.
What is a low carb diet? Who sets the baseline for the ideal amount of grams of carbs consumed per day? I never understood this. I can see how people may argue for and against "low carb" diets, but what I fail to understand is how anybody can argue _for_ a diet higher in carbs supplied by cereal grain-based products like breads, cookies, cakes, muffins, pasta, etc and sugar. Following this logic, isn't every diet that consists of real food -- not heavily processed -- low in carbs? Honestly, how many cups of broccoli and kale can one eat to reach even 100g of carbs per day?
Note: by heavily processed, I mean foods like sugar and refined flours that are borne out of taking a whole plant, extracting only the palatable component, and repeating this process millions of times until you have enough of the component to package it. I wonder how those who eat higher carb diets rich in starchy tubers and rice fare versus those who eat high carb diets rich in dinner rolls, glasses of OJ, cereal, and flavored low fat yogurt.
There are a few different thresholds, and the quality of the carbs (glycemic index / glycemic load) also matters.
Generally a good starting point is the Zone Diet macro split: 40% carb, 30% protein, 30% fats, by calories. On a 2000 cal/day diet, that's roughly 800 calories (or 200g) carbs. Low carb is generally anything less than that, with < 100g being fairly seriously constrained, and ketogenesis generally requiring ~50-100g.
And yes, most unprocessed diets are reasonably low in carbs, or at least have slow carbs. Though there are some relatively high-carb indigenous diets, particularly among Pacific Islanders eating manioc and breadfruit, though fish and seafood are also staples.
The key driver of modern obesity is the high availability of varied and intensely pleasing flavors. Even thirty years ago food was more bland, and there was way less variety in the grocery store. 100 years ago cooking with spices was a rare treat. Animals get fat on what is called the "cafeteria" diet, where they are presented with the choice of a high variety of flavors and nutrients. They do not get fat when presented with a monotonous diet.
Low carb dieting works because you are reducing food reward by removing pleasant starchy and sweet flavors, so people eat less. Low fat dieting also works for the same reason; people have had success by eating mostly plain potato.