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> However, low leptin levels causes the body to enter starvation mode, and hardcore dieting causes leptin levels to drop further. What about fasting? Dr Jason

by voisin 3y ago

> However, low leptin levels causes the body to enter starvation mode, and hardcore dieting causes leptin levels to drop further. What about fasting? Dr Jason Fung wrote a book about fasting that IIRC says that it does not cause starvation mode.

thefz 3y ago
Agree, straying from thermodynamics is wrong. Human fat holds around 8000Kcal per Kg. Stop eating altogether. Every the 8000th Kcal more or less you would have lost 1Kg of fat.
- waterheater 3y ago
  My reply to him addresses this. Intermittent fasting works better than starvation.
- Toutouxc 3y ago
  There’s the issue of not being able to decide what gets burnt. I’ve read that under certain circumstances, the body can actually burn the muscles faster than it burns the fat. Which obviously makes exercise harder.
  - com2kid 3y ago
    When losing weight, about 75% fat and 25% muscle is lost, with a ton of variables being in there (exercise routine, how much muscle you have, what your diet looks like, etc). Lots of arguments about what diets maintain the most muscle (e.g. fasting people say they keep the most muscle, and as much as I love fasting, plenty of studies say that is probably not true.)
  - thefz 3y ago
    Why would the body touch anything else when it has a preferential energy storage?
    - agos 3y ago
      because the body is not a perfect machine. If it were, all this discussion would be moot
- aantix 3y ago
  It's not always going to be fat. The dramatic weight loss induced by GLP-1's demonstrates that. We're seeing a disproportionate amount of lean muscle mass loss.
- gilbetron 3y ago
  The problem is that it is overly simplistic. It is similar to saying "running a marathon is just a thermodynamic problem, expend 2500 calories in a single direction and you can do a marathon." Sure, that's true, but that's not the hard part. Existing at a caloric delta long enough to meet your goal is the problem!
waterheater 3y ago
Just looked up his book "The Obesity Code"; not sure if that's the one you're thinking of. Dr. Fung says obesity is a basically a hormonal issue, not a caloric issue. He discusses a "causality test": "If we inject this hormone into people, they must gain weight". According to Dr. Fung, leptin and ghrelin don't pass this test, but insulin and cortisol do. Still, leptin and insulin appear to have a close relationship. "Insulin promotes fat storage. Leptin reduces fat storage. High levels of insulin should naturally act as an antagonist to leptin. However, the precise mechanisms by which insulin inhibits leptin are yet unknown." He also says that "too much insulin causes obesity" and that "obesity is a state of leptin resistance." (Sorry for that mini book review; I needed to understand what he was saying.) On the fasting point, he's explicitly supportive not of regular fasting but intermittent fasting: "Diets must be intermittent, not steady...we cannot fast all the time. It won't work." Based on my fast read of his work and my own understanding, intermittent fasting keeps leptin levels high enough that the body doesn't kick into calorie restricting mode. One approach which seems to accomplish this is eating close-to-zero carbs five days/week (say, during the week) and then eating lots of carbs two days/week (say, on the weekend). The burst of carbs will cause leptin levels to spike since the body now has tons of available energy. Over the week, the leptin levels will remain elevated, but since you're minimizing carbs, the body will draw energy from adipose tissue.
- paulpauper 3y ago
  Then why are so many people who are insulin resistant overweight? Yet people with type 1 diabetes tend to be thin. I don't think the connection between insulin and weight is well known, assuming one even exists. It's a basic CICO problem. Whether there is insulin resistance or sensitivity does not change this much. IF his theories actually worked, they would work on general population at fixing obesity, but there is scant evidence it does. Like Tabues and others, he built a career on some theory that falls short when applied to real people in controlled setting.
  - waterheater 3y ago
    According to this article [1], many people with type 1 diabetes are also overweight. In fact, the article cites a research study showing that, for those with type 1 diabetes, higher blood glucose levels corresponded to higher weight gain. Clearly, this weight gain isn't CICO-related but is actually related carbohydrates. As far as I understand, people with type 2 diabetes (insulin resistance) have excess glucose in their bloodstream, which becomes easily stored as body fat. Type 2 diabetes seems particularly caused by eating excessive amounts of carbs over a long period of time. In both cases, excessive carbs leads to obesity. The type of calories matters more for obese people trying to lose weight than for healthy people maintaining their weight. [1] https://www.dbl-diabetes.com/all-about-diabetes/food/type-1-diabetes-insulin-weight-gain https://www.dbl-diabetes.com/all-about-diabetes/food/type-1-...

by voisin 3y ago

thefz 3y ago

Agree, straying from thermodynamics is wrong. Human fat holds around 8000Kcal per Kg. Stop eating altogether. Every the 8000th Kcal more or less you would have lost 1Kg of fat.

waterheater 3y ago
My reply to him addresses this. Intermittent fasting works better than starvation.
Toutouxc 3y ago
There’s the issue of not being able to decide what gets burnt. I’ve read that under certain circumstances, the body can actually burn the muscles faster than it burns the fat. Which obviously makes exercise harder.
- com2kid 3y ago
  When losing weight, about 75% fat and 25% muscle is lost, with a ton of variables being in there (exercise routine, how much muscle you have, what your diet looks like, etc). Lots of arguments about what diets maintain the most muscle (e.g. fasting people say they keep the most muscle, and as much as I love fasting, plenty of studies say that is probably not true.)
- thefz 3y ago
  Why would the body touch anything else when it has a preferential energy storage?
  - agos 3y ago
    because the body is not a perfect machine. If it were, all this discussion would be moot
aantix 3y ago
It's not always going to be fat. The dramatic weight loss induced by GLP-1's demonstrates that. We're seeing a disproportionate amount of lean muscle mass loss.
gilbetron 3y ago
The problem is that it is overly simplistic. It is similar to saying "running a marathon is just a thermodynamic problem, expend 2500 calories in a single direction and you can do a marathon." Sure, that's true, but that's not the hard part. Existing at a caloric delta long enough to meet your goal is the problem!

waterheater 3y ago

Just looked up his book "The Obesity Code"; not sure if that's the one you're thinking of. Dr. Fung says obesity is a basically a hormonal issue, not a caloric issue. He discusses a "causality test": "If we inject this hormone into people, they must gain weight". According to Dr. Fung, leptin and ghrelin don't pass this test, but insulin and cortisol do. Still, leptin and insulin appear to have a close relationship. "Insulin promotes fat storage. Leptin reduces fat storage. High levels of insulin should naturally act as an antagonist to leptin. However, the precise mechanisms by which insulin inhibits leptin are yet unknown." He also says that "too much insulin causes obesity" and that "obesity is a state of leptin resistance." (Sorry for that mini book review; I needed to understand what he was saying.) On the fasting point, he's explicitly supportive not of regular fasting but intermittent fasting: "Diets must be intermittent, not steady...we cannot fast all the time. It won't work." Based on my fast read of his work and my own understanding, intermittent fasting keeps leptin levels high enough that the body doesn't kick into calorie restricting mode. One approach which seems to accomplish this is eating close-to-zero carbs five days/week (say, during the week) and then eating lots of carbs two days/week (say, on the weekend). The burst of carbs will cause leptin levels to spike since the body now has tons of available energy. Over the week, the leptin levels will remain elevated, but since you're minimizing carbs, the body will draw energy from adipose tissue.

paulpauper 3y ago
Then why are so many people who are insulin resistant overweight? Yet people with type 1 diabetes tend to be thin. I don't think the connection between insulin and weight is well known, assuming one even exists. It's a basic CICO problem. Whether there is insulin resistance or sensitivity does not change this much. IF his theories actually worked, they would work on general population at fixing obesity, but there is scant evidence it does. Like Tabues and others, he built a career on some theory that falls short when applied to real people in controlled setting.
- waterheater 3y ago
  According to this article [1], many people with type 1 diabetes are also overweight. In fact, the article cites a research study showing that, for those with type 1 diabetes, higher blood glucose levels corresponded to higher weight gain. Clearly, this weight gain isn't CICO-related but is actually related carbohydrates. As far as I understand, people with type 2 diabetes (insulin resistance) have excess glucose in their bloodstream, which becomes easily stored as body fat. Type 2 diabetes seems particularly caused by eating excessive amounts of carbs over a long period of time. In both cases, excessive carbs leads to obesity. The type of calories matters more for obese people trying to lose weight than for healthy people maintaining their weight. [1] https://www.dbl-diabetes.com/all-about-diabetes/food/type-1-diabetes-insulin-weight-gain https://www.dbl-diabetes.com/all-about-diabetes/food/type-1-...