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by
Jason Fung
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December 29, 2023 - January 11, 2024
With the model of the calorie-balancing scale, we assume that fat gain or loss is essentially unregulated, and that weight gain and loss is under conscious control. But no system in the body is unregulated like that.
The problem of fat accumulation is really a problem of distribution of energy.
What we find instead is that a sudden reduction of Calories In causes a similar reduction in Calories Out, and no weight is lost as the body balances its energy budget.
A 30 percent reduction in caloric intake resulted in a nearly identical 30 percent reduction in caloric expenditure.
The key assumption of the theory that reducing caloric intake leads to weight loss is false, since decreased caloric intake inevitably leads to decreased caloric expenditure.
Losing weight triggers two important responses. First, total energy expenditure is immediately and indefinitely reduced in order to conserve the available energy. Second, hormonal hunger signaling is immediately and indefinitely amplified in an effort to acquire more food. Weight loss results in increased hunger and decreased metabolism.
it is harder for people who have lost weight to resist food.15
Eating less does not result in lasting weight loss. It. Just. Does. Not. Work.
whether physical activity increases or decreases, it has virtually no relationship to the prevalence of obesity.
It is highly improbable that decreased exercise played any role in causing obesity in the first place.
The overwhelming majority of total energy expenditure is not exercise but the basal metabolic rate: metabolic housekeeping tasks
Exercise is still healthy and important—just not equally important. It has many benefits, but weight loss is not among them.
caloric intake increases in response to exercise—we just eat more following a vigorous workout.
You cannot make up for dietary indiscretions by increasing exercise. You can’t outrun a poor diet.
Exercise represents a stress on the body. Small amounts are beneficial, but excessive amounts are detrimental.17
The overfeeding paradox is that excess calories alone are not sufficient for weight gain—in contradiction to the caloric-reduction theory.
Total energy expenditure, comprising mostly basal metabolic rate, is not constant, but varies considerably in response to caloric intake.
The problem in obesity is that the set point is too high.
Eating more is not the cause of weight gain but instead the consequence. Eating more does not make us fat. Getting fat makes us eat more. Overeating was not a personal choice. It is a hormonally driven behavior—a natural consequence of increased hunger hormones. The question, then, is what makes us fat in the first place. In other words, why is the body set weight so high?
Diets work well at the start, but as we lose weight, our metabolism slows. Compensatory mechanisms start almost immediately and persist almost indefinitely.
The smarter solution is to identify the body’s homeostatic mechanism and adjust it downward—and there lies our challenge. Since obesity results from a high body set weight, the treatment for obesity is to lower it. But how do we lower our thermostat?
Higher levels of fat tissue produce higher levels of leptin. Traveling to the brain, it turns down hunger to prevent further fat storage.
The vast majority of obese people are not deficient in leptin. Their leptin levels are high, not low. But these high levels did not produce the desired effect of lowering body fatness. Obesity is a state of leptin resistance.
Excess calories did not cause obesity, so reduced calories could not cure it. Lack of exercise did not cause obesity, so increased exercise could not cure it. The false gods of the caloric religion had been exposed as charlatans.
The other major problem with obesity research is that it fails to take into account that obesity is a time-dependent disease. It develops only over long periods, usually decades.
Obesity is a hormonal dysregulation of fat mass. The body maintains a body set weight, much like a thermostat in a house. When the body set weight is set too high, obesity results.
OBESITY IS NOT caused by an excess of calories, but instead by a body set weight that is too high because of a hormonal imbalance in the body.
Hormones are molecules that deliver messages to a target cell. For example, thyroid hormone delivers a message to cells in the thyroid gland to increase its activity. Insulin delivers the message to most human cells to take glucose out of the blood to use for energy.
Insulin is a key regulator of energy metabolism, and it is one of the fundamental hormones that promote fat accumulation and storage.
mealtimes, ingested carbohydrate leads to more glucose being available than needed.
We store this glucose by turning it into glycogen in the liver—a process called glycogenesis.
But the liver has only limited storage space for glycogen. Once full, excess carbohydrates will be turned into fat—a process called de novo lipogenesis. (De novo means “from new.” Lipogenesis means “making new fat.”
Glycogen is easily available, but in limited supply. During a short-term fast (“fast” meaning that you do not eat), your body has enough glycogen available to function. During a prolonged fast, your body can make new glucose from its fat stores—a process called gluconeogenesis (the “making of new sugar”). Fat is burned to release energy, which is then sent out to the body—the fat-storage process in reverse.
Normally, this well-designed, balanced system keeps itself in check. We eat, insulin goes up, and we store energy as glycogen and fat. We fast, insulin goes down and we use our stored energy.
If you continually refill your glycogen stores, you never need to use your fat stores for energy.
The key to understanding obesity is to understand what regulates body set weight, why body set weight is set so high, and how to reset it lower.
In this hypothesis, high insulin levels increase the body set weight.
research reveals a close association between high fasting insulin levels and obesity,
A recent study29 suggests that 75 percent of the weight-loss response in obesity is predicted by insulin levels. Not willpower. Not caloric intake. Not peer support or peer pressure. Not exercise. Just insulin.
We get fat because our body set weight thermostat is set too high. Why? Because our insulin levels are too high.
A critical physiological variable such as body fatness is not left up to the vagaries of daily caloric intake and exercise. Instead, hormones precisely and tightly regulate body fat. We don’t consciously control our body weight any more than we control our heart rates, our basal metabolic rates, our body temperatures or our breathing.
Obesity is a hormonal dysregulation of fat accumulation.
Both fasting insulin and fasting leptin levels are higher in obese people, indicating a state of both insulin and leptin resistance.
The question is not how to balance calories; the question is how to balance our hormones. The most crucial question in obesity is how to reduce insulin.
Therefore, the hormonal theory of obesity takes shape: chronically high cortisol raises insulin levels, which in turn leads to obesity.
Long-term stress leads to long-term elevated cortisol levels, which leads to extra pounds.
Population studies consistently link short sleep duration and excess weight,
Getting enough good sleep is essential to any weight loss plan.
While the Mediterranean diet held its own against the powerful, fat-reducing Atkins diet, the low-fat AHA standard was left choking in the dust—sad, tired and unloved, except by academic physicians.
What was the best diet for maintaining metabolism? The very-low-carbohydrate diet. This diet also seemed to reduce appetite.
