Having studied this for some 20 years, I too am pretty convinced that "calories in, calories out" is little more than naive thinking. That's just not how the body works.
Yes, often you'll hear things like "studies show that approx. 20 % are successful at weight loss". But the definition of weight loss in those studies tends to be something like "maintained a weight loss of 5 kg or more after 5 years." Since one's weight can easily fluctuate +-1,5 kg during the course of the day, that should feel a bit underwhelming. And that's not even the whole truth, or anything even near the truth —
If you look at people who have a lost a significant amount of weight (20-40 kg), the success rate drops to essentially zero (<1%). So as far as studies can tell, it seems to be very difficult, if not impossible, to lose a large amount of weight by calorie deficit alone. The body seems to have a set point weight that it still prefers years and years after significant weight loss.
In fact, even gastric bypass patients often gain back a significant amount of weight 5-10 years after surgery. And those people people typically can't eat sugary foods, because it makes them ill, and they can only eat very very small portions (the stomach is reduced to the size of a lemon). Still they somehow manage to gain weight!
In fact, I have a hypothesis that very low calorie diets are one of the CAUSES of morbid obesity. People who go on VLCDs tend to follow a cycle whereby they lose around 10–20 % of body weight and then gain back around 15–30 % within 2-3 years. Repeat that a few cycles, and an overweight person will quickly be morbidly obese.
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Having studied this for some 20 years, I too am pretty convinced that "calories in, calories out" is little more than naive thinking. That's just not how the body works.
Yes, often you'll hear things like "studies show that approx. 20 % are successful at weight loss". But the definition of weight loss in those studies tends to be something like "maintained a weight loss of 5 kg or more after 5 years." Since one's weight can easily fluctuate +-1,5 kg during the course of the day, that should feel a bit underwhelming. And that's not even the whole truth, or anything even near the truth —
If you look at people who have a lost a significant amount of weight (20-40 kg), the success rate drops to essentially zero (<1%). So as far as studies can tell, it seems to be very difficult, if not impossible, to lose a large amount of weight by calorie deficit alone. The body seems to have a set point weight that it still prefers years and years after significant weight loss.
In fact, even gastric bypass patients often gain back a significant amount of weight 5-10 years after surgery. And those people people typically can't eat sugary foods, because it makes them ill, and they can only eat very very small portions (the stomach is reduced to the size of a lemon). Still they somehow manage to gain weight!
In fact, I have a hypothesis that very low calorie diets are one of the CAUSES of morbid obesity. People who go on VLCDs tend to follow a cycle whereby they lose around 10–20 % of body weight and then gain back around 15–30 % within 2-3 years. Repeat that a few cycles, and an overweight person will quickly be morbidly obese.
Its probably better represented as calories absorbed vs calories expended.