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Comment by lonewolf_ninja | Hacker News Reader

The only effective way for weight loss is making sure that one's caloric intake is less than the amount of calories they burn. And the only way of achieving that is diet and exercise.

Also comparing the human body/brain to a car/mechanical device would be incorrect and is probably an apple to oranges comparison.

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Calories in - calories out is true, but it's hard to measure either with any much accuracy. You can get close with calories in, but measuring calories out isn't easy: There are charts for different activities, but our bodies are not perfect efficient machines that always use the same amount of energy for the same tasks.

Additionally, our bodies can make subtle changes in response to caloric intake: If you ingest fewer calories, you may fidget less, possibly lowering your caloric use more than you lowered your input.

>And the only way of achieving that is diet and exercise

Or increasing the metabolic rate. Or decreasing the calorie storage rate.

Doesn't increasing your metabolic rate require increasing your body temperature? This is something that has always puzzled me when I hear that some people have faster or slower metabolism than others.

Your metabolic rates at birth, adolescence, or your teen years are probably drastically different than your rate now if you're past 30. Is your average body temperature way less than 98.7 now?

Body volume scales roughly with the third power of height, while body surface scales roughly with the second power. Therefore, it is possible for the body temperature to stay constant if the basic metabolic rate (i.e., heat generation) per unit of volume decreases between birth and adulthood.

Besides, the human body has several ways of regulating core body temperature: sweating, restricting blood flow to extremities, goose bumbs, and putting on different clothes.

All good points. Do we have measured values for metabolic rate per unit volume as a function of age? This does seem plausible -- building a new body should take more stuff than maintaining an old body.

But I wonder if this translates into different adults saying that they have fast or slow metabolism as an explanation for their weight.

Perhaps I just don't understand what "metabolic rate" means. My body is a metabolic zero-sum game, unless I'm gaining or losing weight. What comes in as food goes out as heat or mechanical work. I suppose a higher heat output could be achieved at constant temperature by sweating more. A larger person (more skin) could of course generate more heat, but the energy has to come from eating more food or being less active.

Do you simply mean that I was gaining weight at birth, adolescence, and teen years? I could agree with that.

"What comes in as food goes out as heat or mechanical work." Or out as undigested food waste. Don't have an answer for you on metabolic rate, just adding the third way food calories can leave your body.

"The only effective way for weight loss is making sure that one's caloric intake is less than the amount of calories they burn."

This is probably true, but a better question is whether this is even important.

One guy said "it's a lot easier for a fat person to become fit than it is for a fat person to become thin."

Generally the press (and maybe scientists, though I'm not so sure about them) seem obsessed with thinness rather than health or fitness.

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