You know it has taken me just under two years to finally drop that niggling "carbs make you fat" thought in the back of my head. This is understandable if the first book around the subject of nutrition I read was Taubes' GCBC. These papers nailed it for me finally.
Understandably keeping insulin levels consistently elevated slows-to-halts fat-oxidation, and I do believe keeping carbohydrate lower may be healthier in terms of lowering glycation, triglycerides et al. (I think the Jaminet's PHD deals with this very well. Which is why I recommend their amount of carbohydrates and increasing for activity levels.)
Anyhow honestly I am trying to understand now why everyone I know who did low-carb lost a stack of weight, and I can only assume we honestly just began eating more lower-calorie nutrient dense foods (less calories overall), became more active, and spent more time out of elevated insulin levels (non-snacking). And no I do not think we were all insulin-resistant. I think we just eat too much and constantly.
All those posts and whiteboard drawings about "carbohydrate spill-over" are then just a load of rubbish. I mean unless I am taking crazy pills the quotes below are basically saying if you don't oxidise dietary fat (say because you are in a high-carb calorie surplus) it ain't the carbs making you fat, it's the fat you are not oxidising.
Moral of the story (in my mind), if you want to put on fat, eat more calories than you expend and make the surplus calories fat and what you don't burn you will hold onto. This doesn't mean getting the majority of your calories from fat is not useful in comparison to carbohydrate, it just means that if you are consuming more calories of fat than your calorific needs you are probably going to hold onto them, and actually not so much from excessive carbohydrate. You just don't burn fat when you eat carbohydrate constantly, so don't dose yourself constantly over the day.
Well I don't post on PH much, but thought this may be useful for those just starting Paleo et al.
"During overfeeding, subjects were given an average of 1398 g carbohydrate and oxidized 1280 g, which resulted in a mean carbohydrate balance of 115 g (Table 4). Concomitant measures of hepatic de novo lipogenesis showed that the mean de novo lipogenesis was 27% (averaged for both overfeeding treatments and for pooled subject data). The estimated amount of absolute fat production via de novo lipogenesis that this represents is only 4 g; however, this may well be an underestimation because these estimates are dependent on an index that was not measured, namely, VLDL-triacylglycerol production. Nonetheless, even when VLDL-triacylglycerol production was measured from kinetic modeling, absolute fat production is similarly low (8). Dietary fat intake during this period was 512 g, of which 233 g was oxidized, leaving all subjects with an average positive fat balance of 278 g (Table 4), of which the de novo lipogenesis contribution was clearly a tiny proportion."
"Additionally, McDevitt et al report that, in all settings, the total de novo lipogenesis flux represented a small fraction of both the surplus carbohydrate energy ingested and the total fat stored in the body. The authors calculated that between 3 and 8 g fat/d was produced through de novo lipogenesis compared with 360???390 g carbohydrate ingested/d and 60???75 g body fat stored/d. Thus, the addition of excess carbohydrate energy to a mixed diet so that total energy intake exceeded total energy expenditure (TEE) increased body fat stores, but not by conversion of the carbohydrate to fat. Instead, the oxidation of dietary fat was suppressed and fat storage thereby increased."
"DNL is not the pathway of first resort for added dietary CHO in humans, at least on Western (high-fat) diets. DNL can occur, but it generally does not. A `functional block' therefore exists between CHO and fat in humans, analogous to the absolute biochemical block in the direction from fat to carbohydrate in all animals. Therefore, the two major macronutrient energy sources are not interconvertible currencies in the mammalian organism; they must be considered separately and are probably regulated independently, by separate signals and toward separate ends."
"When a diet of mixed macronutrient composition is eaten to excess, the carbohydrate is preferentially burned off, while the fat is mostly shunted into fat tissue. This makes sense, because why would the body go through the inefficient process of converting carbohydrate to fat for storage when it can just shunt dietary fat directly into fat tissue? This does not imply that dietary fat is fattening under conditions of energy balance."
"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. Here, the quantitative importance of DNL in humans is reviewed, focusing on the response to increased intake of dietary CHO. Eucaloric replacement of dietary fat by CHO does not induce hepatic DNL to any substantial degree. Similarly, addition of CHO to a mixed diet does not increase hepatic DNL to quantitatively important levels, as long as CHO energy intake remains less than total energy expenditure (TEE). Instead, dietary CHO replaces fat in the whole-body fuel mixture, even in the post-absorptive state. Body fat is thereby accrued, but the pathway of DNL is not traversed; instead, a coordinated set of metabolic adaptations, including resistance of hepatic glucose production to suppression by insulin, occurs that allows CHO oxidation to increase and match CHO intake. Only when CHO energy intake exceeds TEE does DNL in liver or adipose tissue contribute significantly to the whole-body energy economy. It is concluded that DNL is not the pathway of first resort for added dietary CHO, in humans. Under most dietary conditions, the two major macronutrient energy sources (CHO and fat) are therefore not interconvertible currencies; CHO and fat have independent, though interacting, economies and independent regulation. The metabolic mechanisms and physiologic implications of the functional block between CHO and fat in humans are discussed, but require further investigation."
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on November 05, 2013
at 08:02 PM
@thhq (sorry comments are broken again - sigh...)
I see the quote you refer to "The authors calculated that between 3 and 8 g fat/d was produced through de novo lipogenesis compared with 360–390 g carbohydrate ingested/d and 60–75 g body fat stored/d. Thus, the addition of excess carbohydrate energy to a mixed diet so that total energy intake exceeded total energy expenditure (TEE) increased body fat stores, but not by conversion of the carbohydrate to fat. Instead, the oxidation of dietary fat was suppressed and fat storage thereby increased."
It's well known that if insulin is high, fat cells do not allow access to their energy stores, thus fat cannot be burned - that seems to be what these studies rediscovered. But for this to happen, you'd eat every few hours to keep it high. It also doesn't negate de-novo lipogenesis - if we didn't have this process, we wouldn't be able to convert carbs (and protein indirectly) into fat. We don't need to use that process to store fat, as, well, it's already fat, so it can simply be stored.
It's also well known that fat doesn't trigger insulin, so if you are eating the proverbial 6 meals/day vs IF, you'll keep insulin up, and thus prevent access to fat stores.
On the flip side, If you do a fairly low-carb diet with IF (16/8), your insulin is kept low for the 16 hours of fasting, despite the possibility of consuming any fats during the fast (though you'll burn less of your own fat stores.)
It's also very difficult to eat a 100% fat diet and overconsume past your TEE - to attempt this will require artificial means: exogenous lipase. Once you exceed your capacity for digesting fats, you'll have a very unpleasant set of repeated trips to the bathroom. It is however possible to overeat past your TEE with carbs using modern artificial food-like products that blunt satiety. (things that start off as crunchy and then turn into liquid as you chew them and have only a little bit of flavor, and aren't filling.) It wouldn't be possible with fruit - the very ideas of eating more than one apple is a huge turn-off.
Or put another way, if you simply don't overeat, you won't get fat.
We also know that if you're constantly spiking your insulin, such as on a very high carb diet, you'll get hungry as the blood is cleared of glucose (and other macros) and will tend to eat again - if your diet is mostly carbs, you'll cycle from hyperglycemic to hypoglycemic (and get hungry and eat again), thus storing lots and lots into your fat cells.
I'm not sure why anyone would see this as "the fat is to blame." Quite frankly, I don't think the carbs are to blame either. These mechanisms are in place to keep us alive and healthy, and if we eat consistently with our evolutionary pathways rather than with the modern SAD, things don't go wrong.
I'm in favor of minimizing carbs for other reasons (glycation, ROS creation, and over-signaling insulin, cancer cell metabolism not being able to use ketones), but this will vary depending on your exercise/performance needs.
If anything these discoveries imply that in an ancestral environment, we rarely had situations were we could feast for many days on end to be able to overfeed by 50% more calories per day; perhaps, at the end of summer, but certainly not all year round. Seasonality counts.
on November 05, 2013
at 04:51 PM
carbohydrates become fat, but so does dietary fat. /shrug
on November 04, 2013
at 10:28 PM
There are some people who can handle higher carbs than others, and others who are very sensitive to carbs and quickly gain fat if they eat too many (and the amount varies from person to person.)
I'm not in favor of a zero carb diet, certainly some seems to be beneficial, but if you choose to go with zero, as long as you have access to enough excess protein, and aren't overly stressed, it's fine.
There are two disposal mechanism: we can either burn it off (you'd go into thermogenesis, or you start twitching or fidgeting more to burn off the calories), or insulin will tell your fat cells to burn it off.
For those with lower muscle mass, they can't dispose of glucose as quickly into glycogen stores, so the only available path is fat stores.
The bugaboo is insulin resistance. At some point, when muscles are full, and fat cells are full and the liver has its stores filled, extra carbs become hard to get rid of. If they don't exercise, or can't fidget, the high blood sugar becomes problematic. Insulin will rise, possibly damaging the pancreatic beta cells since they constantly pump more and more insulin, and the only disposal mechanism becomes the kidneys which suffer quite a lot of damage shunting glucose out to urine. Mind you, if someone reaches this point, they are metabolically damaged.
The hardest hit by diabetes are those who have been skinny their entire lives and as they age become insulin resistant. Since they can't gain fat, their diabetes is far more serious as their fat cells were always resistant, now they no longer have a way to dispose of glucose.
There are also known issues with higher carbs and AGEs (protein-glucose-glycation), which literally ages us and damages joint, skin, and other lean tissues — even without metabolic syndrome issues.
Additionally, when mitochondria, which burn glucose, they create ROS (reactive-oxygen species, aka free radicals), which consume antioxidants. When mitochondria burn fats, no ROS are created; thus, burning fat is far more "clean" and less harmful.
Higher carb intake is also associated with the dense LDL pattern, which may or may not be an issue.
Now lifestyle factors are going to be a huge issue. Certain types of sports outright require burning more carbs, e.g. the person doing Crossfit 5x a week certainly will need extra carbs compared to, say, a sprinter that occasionally sprints, or someone who lifts weights.
IMO, go as low carb as you can based on your needs in order to have a longer, healthier life, based on your performance needs.
on November 04, 2013
at 10:25 PM
"Moral of the story (in my mind), if you want to put on fat, eat more calories than you expend and make the surplus calories fat and what you don't burn you will hold onto"
you mentioned Jaminet...your statement above kinda gels with the Jaminet diet 'tweaked' for weight loss, here's some text from his web site,
"Eat Protein and Carbs; Reduce Fat. This may surprise many readers, since we’re fat-friendly, but there should be no reduction in carb or protein consumption on weight loss diets. Calorie restriction should come out of fat." Paul Jaminet. you can read the full Jaminet post here: Perfect Health Diet: Weight Loss Version. Feb 2011
edit: i should just clarify, the Jaminet 'weight loss version' diet is still Not low fat, it is just reduced fat as compared to their 'default' guidelines. "Our (weight loss) diet is not low fat. Even at 1200 calories, it includes typically 500 fat calories in order to get key fat-associated nutrients. We are suggesting reducing fat compared to a high-fat baseline." Paul Jaminet comment
another thought on the statement "...if you want to put on fat, eat more calories than you expend and make the surplus calories fat and what you don't burn you will hold onto"...
this could also be an explanation why some people start gaining body fat after reintroducing carbs, like potatoes & white rice, post zc/vlc...because they just add these foods back into their diet with no reduction in other macros to compensate for the increase in calories.
on November 04, 2013
at 08:22 PM
All this makes sense. Our bodies store fat. If we consume carbohydrates, they must either metabolized for energy or converted to fat and stored. This is upstream of fat in the scheme of things. Fat must then be metabolized for energy or stored. If energy needs are met by carbohydrate consumption, then fat is stored. If energy needs are met with a fraction of the carbohydrate consumption, then the remainder is converted to and stored as fat.
Where the excess comes from cannot be identified. Heck, because carbs are metabolized at a faster rate then fats, you could take the position that fats are always to blame.
on November 04, 2013
at 07:00 PM