Carbs to fat

[Stella]

Jeff,

I've read and heard Dr McD talk about how the body will not convert carbs to fat unless under extraordinary circumstances. Unless it's fructose esp. HFC. Yet it seems that every nutritionist, dietician or Dr is saying the opposite out there.(present company excluded) I've heard that all carbs are quickly turned to sugar and then fat at least 3 times this week alone. Including most recently Dr Oz. He made a point of saying this doesn't happen with protein that it takes too many calories to convert it.
Now I understand what happens to protein, esp. animal protein, when we eat too much and I don't want that either.

To my question. Is this statement Dr McD made still hold true scientifically? Why do more people not know this and why do so many "professionals" still believe the opposite. Is there new science on this subject?
My Dr. the other day told me to lay off the potatoes that's what was causing my weight to stall. I told her that my calories were still under 1500 a day and she said it didn't matter if I was eating all that sugar!
I don't eat sugar. I'm very confused.

TIA
Stella

[JeffN]

Greetings,

All excess calories, from either fat, protein or carb, can eventually be stored as fat. While it may not be the preference for the body to do this when carbs are in excess, as it is not an easy conversion as it is for fat, if it continues over time, and in enough excess, they will be stored.

http://drmcdougall.com/forums/viewtopic.php?t=13772

However, if weight is an issue, I would recommend you review the threads on calorie density, and the Maximum Weight Loss program and to make sure you are following the principles. If so, time and adherence will be the most important factors.

In Health
Jeff

[Stella]

I just listened to a podcast lecture by Dr McD and he said that humans lacked the ability to convert excess carbs to fat. I think he called it denovolipogenesis or something of the sort.
I have been following the MWL for almost 4 weeks with no weight loss and using CRON tracking. I was doing the regular program before and lost ten then stalled. I've been between 1300-1500 calories a day with regular exercise. I've recently had blood work done and am waiting to hear if it might be thyroid issues. If not (hope not) then I will continue with "time and adherence" and assume things will happen in their own time. One month in a life span is not much. I have been using the threads on calorie density to be sure. Those helped me with my love of bread.

Thanks again,
Stella

[JeffN]

that humans lacked the ability to convert excess carbs to fat. I think he called it denovolipogenesis or something of the sort.

Correct, but only during short term overfeeding because it is more efficient for the body to burn those calories off as heat, rather than convert them. However, if it is continued over time with enough excess, the body will store excess carbs as fat.

Eur J Clin Nutr. 1999 Apr;53 Suppl 1:S53-65. De novo lipogenesis in humans: metabolic and regulatory aspects. Hellerstein MK.

"The enzymatic pathway for converting dietary carbohydrate (CHO) into fat, or de novo lipogenesis (DNL), is present in humans, whereas the capacity to convert fats into CHO does not exist."

Fat and carbohydrate overfeeding in humans: different effects on energy storage. Randomized controlled trial
Horton TJ, et al. Am J Clin Nutr. 1995.

http://www.ncbi.nlm.nih.gov/m/pubmed/7598063/
Abstract
Both the amount and composition of food eaten influence body-weight regulation. The purpose of this study was to determine whether and by what mechanism excess dietary fat leads to greater fat accumulation than does excess dietary carbohydrate. We overfed isoenergetic amounts (50% above energy requirements) of fat and carbohydrate (for 14 d each) to nine lean and seven obese men. A whole-room calorimeter was used to measure energy expenditure and nutrient oxidation on days 0, 1, 7, and 14 of each overfeeding period. From energy and nutrient balances (intake-expenditure) we estimated the amount and composition of energy stored. Carbohydrate overfeeding produced progressive increases in carbohydrate oxidation and total energy expenditure resulting in 75-85% of excess energy being stored. Alternatively, fat overfeeding had minimal effects on fat oxidation and total energy expenditure, leading to storage of 90-95% of excess energy. Excess dietary fat leads to greater fat accumulation than does excess dietary carbohydrate, and the difference was greatest early in the overfeeding period



Glycogen storage capacity and de novo lipogenesis during massive carbohydrate overfeeding in man.
Acheson KJ, et al. Am J Clin Nutr. 1988.

http://www.ncbi.nlm.nih.gov/m/pubmed/3165600/
Abstract
The metabolic balance method was performed on three men to investigate the fate of large excesses of carbohydrate. Glycogen stores, which were first depleted by diet (3 d, 8.35 +/- 0.27 MJ [1994 +/- 65 kcal] decreasing to 5.70 +/- 1.03 MJ [1361 +/- 247 kcal], 15% protein, 75% fat, 10% carbohydrate) and exercise, were repleted during 7 d carbohydrate overfeeding (11% protein, 3% fat, and 86% carbohydrate) providing 15.25 +/- 1.10 MJ (3642 +/- 263 kcal) on the first day, increasing progressively to 20.64 +/- 1.30 MJ (4930 +/- 311 kcal) on the last day of overfeeding. Glycogen depletion was again accomplished with 2 d of carbohydrate restriction (2.52 MJ/d [602 kcal/d], 85% protein, and 15% fat). Glycogen storage capacity in man is approximately 15 g/kg body weight and can accommodate a gain of approximately 500 g before net lipid synthesis contributes to increasing body fat mass. When the glycogen stores are saturated, massive intakes of carbohydrate are disposed of by high carbohydrate-oxidation rates and substantial de novo lipid synthesis (150 g lipid/d using approximately 475 g CHO/d) without postabsorptive hyperglycemia.

I have been following the MWL for almost 4 weeks with no weight loss and using CRON tracking. I was doing the regular program before and lost ten then stalled. I've been between 1300-1500 calories a day with regular exercise. I've recently had blood work done and am waiting to hear if it might be thyroid issues. If not (hope not) then I will continue with "time and adherence" and assume things will happen in their own time. One month in a life span is not much. I have been using the threads on calorie density to be sure. Those helped me with my love of bread.

Thyroid can be an issue so it is important to make sure you have that checked out.

While the MWL is set up so most anyone will lose weight at around 1% of their weight per week on average (about 1-3 lbs per week), you may have to make some minor adjustments to the MWL program to fit your specific needs.

I discuss these adjustments in this thread..

http://drmcdougall.com/forums/viewtopic.php?t=11186

Remember, the focus of the MWL plan is calorie density and not calories. Therefore, counting calories is not part of MWL because it shifts the focus back to calories and not calorie density.

In Health
Jeff

[hazelrah]

"The enzymatic pathway for converting dietary carbohydrate (CHO) into fat, or de novo lipogenesis (DNL), is present in humans, whereas the capacity to convert fats into CHO does not exist."

...

In Health
Jeff

So how do we lose the fat that has accumulated? I remember hearing once that we never lose the fat cells when we lose weight, we only dehydrate those cells. Can you explain the mechanics of weight loss so that even I can understand it?

Thanks,

Mark

[JeffN]

"The enzymatic pathway for converting dietary carbohydrate (CHO) into fat, or de novo lipogenesis (DNL), is present in humans, whereas the capacity to convert fats into CHO does not exist."

...

In Health
Jeff

So how do we lose the fat that has accumulated? I remember hearing once that we never lose the fat cells when we lose weight, we only dehydrate those cells. Can you explain the mechanics of weight loss so that even I can understand it?

Thanks,

Mark

Sure.

When caloric output is greater than caloric intake, we burn off body fat for heat/energy. The human body can burn fat as fat (fatty acids), and does not have to be able to convert it to carb to be burned.

In Health
Jeff

[hazelrah]

Sure.

When caloric output is greater than caloric intake, we burn off body fat for energy. The human body can burn fat as fat (fatty acids), and does not have to be able to convert it to carb to be burned.

In Health
Jeff

That was so simple! Are those fatty acids a lot less appealing (efficient) to the muscles as energy? Things sure seem to run a lot easier when carbs are taken in. Maybe it's just because when the body is running on the fatty acids there are no carbs for the brain, so it is more uncomfortable?

Thank you very much for the insight!

Mark

[JeffN]

Sure.

When caloric output is greater than caloric intake, we burn off body fat for energy. The human body can burn fat as fat (fatty acids), and does not have to be able to convert it to carb to be burned.

In Health
Jeff

That was so simple! Are those fatty acids a lot less appealing (efficient) to the muscles as energy? Things sure seem to run a lot easier when carbs are taken in. Maybe it's just because when the body is running on the fatty acids there are no carbs for the brain, so it is more uncomfortable?

Thank you very much for the insight!

Mark

The body is usually running on a fuel mix of about 50% glucose and about 50% fat when at rest and low activity. At higher activity and intensity levels, the amount of total calories expended goes up and the percentage of fuel from glucose goes up (as it is more efficient and quicker to burn) but the percentage of fuel from fat goes down. These fatty acids we are burning come from a mixture of our stored fats and the fats we have ingested.

In Health
Jeff

[hazelrah]

This is really interesting. It helps a lot of things I heard/read when I was running marathons in the 80s coalesce. Thanks.

By the way, the '87 LA marathon, which was my first marathon, completely changed my life. It may be why I'm here today. I tried to adhere to Pritikin in those days. In fact, I wonder if I would have been able to actually complete it if I hadn't tried to adhere to the Pritikin principles as well as I could. I wanted to thank you for whatever you may have done to contribute to that plan and promote it.

I am just now getting back to where my running training involves building muscle more than trying to heal my damaged cardiovascular system. I reached a tipping point about 10 years ago and I would feel like taking a nap 20 minutes into a jog. After listening to Dr. McDougall for a year or two, it finally dawned on me that my problems had to do with my arteries and blood vessels. I came here hoping to get my running back to a place where it could enhance my life again, and, in the last few months, it seems to be doing just that. I just wanted to let you know that I feel pretty lucky to have bumped into you(twice!) to advise and contribute to my approach to diet for the last 30 years or so. Thank you for doing such a good job against tremendous odds, both at Pritikin and here.

Mark

[vgpedlr]

I know exactly what you mean, Mark. I have found that this eating plan makes it so much easier to train, recover and race than the way I ate before. Previously, I tried a horrific hodge podge of gourmet organic foodie-ness with unfounded sports "nutrition" and supplements with little success. Now I understand why: my tank was never full because I ate way too much fat and protein, while consistently emptying my carbohydrate stores. My energy is much more consistent and I'm always motivated to train. I can see the same low energy in people around me and I want to shake them and tell them! Alas, they already look at me funny with all my baked potatoes...

[bkcham85]

Jeff wrote:

The body is usually running on a fuel mix of about 50% glucose and about 50% fat when at rest and low activity. At higher activity and intensity levels, the amount of total calories expended goes up and the percentage of fuel from glucose goes up (as it is more efficient and quicker to burn) but the percentage of fuel from fat goes down. These fatty acids we are burning come from a mixture of our stored fats and the fats we have ingested.

Is this accurate? Where's the reference?

Also:
All excess calories, from either fat, protein or carb, can eventually be stored as fat. While it may not be the preference for the body to do this when carbs are in excess, as it is not an easy conversion as it is for fat, if it continues over time, and in enough excess, they will be stored.

Protein can be converted to fat?

[JeffN]

The body is usually running on a fuel mix of about 50% glucose and about 50% fat when at rest and low activity. At higher activity and intensity levels, the amount of total calories expended goes up and the percentage of fuel from glucose goes up (as it is more efficient and quicker to burn) but the percentage of fuel from fat goes down. These fatty acids we are burning come from a mixture of our stored fats and the fats we have ingested.

Is this accurate? Where's the reference?

Technically speaking, it can never be 100% accurate as the type of fuel used and the rate at which it is utilized during exercise is dependent on several factors including the intensity and duration of the exercise. The 50/50 is a rough estimate often used and may actually be a slightly higher percent of fat at rest and at very low intensity of exercise. And, as intensity increases, the shift is to a higher percentage of calories from carb/glucose.

Indirect calorimeter and respiratory quotient is the method often used to determine these percentages.

http://www.ncbi.nlm.nih.gov/sites/entre ... uid=838636

http://www.ncbi.nlm.nih.gov/sites/entre ... id=9804587

All excess calories, from either fat, protein or carb, can eventually be stored as fat. While it may not be the preference for the body to do this when carbs are in excess, as it is not an easy conversion as it is for fat, if it continues over time, and in enough excess, they will be stored.

Protein can be converted to fat?

Not directly.

All excess calories, whether from fat, protein or carb can "eventually" be stored as fat. While none of the conversions happen directly, excess intake of any of the macronutrients can "eventually" be stored as fat as part of the overall process of metabolism.

As we see below, excess protein is broken down into amino acids which then can be metabolized to glycogen or fat and subsequently used for energy metabolism.





In addition, we can also see how carb can be converted to fat, though also not directly, as part of the overall process of metabolism.

In Health
Jeff

[bkcham85]

Thanks for the info. I really want to know about this.

I guess I just have it stuck in my mind Dr. McDougall saying "The fat you eat is the fat you wear". And he also frequently says that carbohydrate is our body's main source of energy; we only use fat for energy when we're starving. I see now that these statements are not correct, from a biochemical point of view. They are a simplified way of presenting calorie density.

Following a McDougall plan would mean getting about 10% of calories from fat. Yet around half the calories we use for energy are derived from fat. Now, I'm far from a genius in math, (trust me) but that doesn't seem to add up!

But if you don't need to lose any weight, where's the fat coming from?

[petero]

But if you don't need to lose any weight, where's the fat coming from?

Well, here's a link to an explanation of lipogenesis: http://www.elmhurst.edu/~chm/vchembook/ ... Afate.html which is an interesting (but difficult ) read.

The most relevant quotes:

Lipid metabolism is in a constant state of dynamic equilibrium. This means that some lipids are constantly being oxidized to meet energy needs, while others are being synthesized and stored. In rats, the average life-time of a single lipid molecule ranges from 2 to 10 days. A similar figure probably applies to human lipid metabolism.

A total of 55% of the carbohydrates [ingested] are involved in the synthesis of fats.

So there is a constant building and destruction of fat all the time. The body is more like a chemical soup rather than an assembly line.

--Peter

[JeffN]

But if you don't need to lose any weight, where's the fat coming from?

Well, here's a link to an explanation of lipogenesis: http://www.elmhurst.edu/~chm/vchembook/ ... Afate.html which is an interesting (but difficult ) read.

The most relevant quotes:

Lipid metabolism is in a constant state of dynamic equilibrium. This means that some lipids are constantly being oxidized to meet energy needs, while others are being synthesized and stored. In rats, the average life-time of a single lipid molecule ranges from 2 to 10 days. A similar figure probably applies to human lipid metabolism.

A total of 55% of the carbohydrates [ingested] are involved in the synthesis of fats.

So there is a constant building and destruction of fat all the time. The body is more like a chemical soup rather than an assembly line.

--Peter

Thanks for posting the link, which explains some of the chemical pathways involved in the earlier diagram I posted.

The reason this sounds confusing to some of us is that to understand all of this we have to understand the very complex process called metabolism, which, as Peter tried to describe, is more like a very fancy, intricate and dynamic "chemical soup" (though I would use the word "process"). It is extremely complicated and involves 10's of 1000's of reactions/conversions etc.

Just as one example of why some of the above math does not work...

If I was to eat 100% calories from carbs, and consumed to many calories, I would still store excess calories as both glycogen (stored sugars) and fat, and when I would exercise at a moderate pace, I would be burning from a mixture of both, fat and carbohydrate. So even though I at a 100% fat free diet, I would still produce and store body fat and burn fat when exercising.

In Health
Jeff