Fat preferred fuel over carbohydrates - Why? (Biochemically) page 2

[Knifegill]

I prefer to think of the macronutrient ratios of hunter-gatherers for inspiration. The body really can do fine on a wide variety of staple foods. There are pathways for both carbohydrate metabolism and fat metabolism and I think it prudent to train both pathways for efficiency. People eat everything they can find. Always have. Just stick to what they've been finding in the wild - and you're miles ahead of the rat race.

I'm a high-fat guy, but I'm also of European and Native American descent, with tendencies toward the autism spectrum - so ketosis is a happy place for me. That might not be true for everyone, so to assert "the body" has a "preferred" source is preposterous.

[Neckhammer]

Mitochondria prefer to burn fat. Most cells have mitochondria. There are no good glucose disposal pathways so overeating it causes health issues. There are only a couple things that are glucose or ketone dependent (brain, red blood cell...). So, eat enough glucose for those cells that need it plus however much more for your particular level of high intensity exercise and get the rest of energy from fat to prevent the problems that arise from too much glucose. Thats the short story.

Oh, and since you asked for links, websites, and books. The above is the predominant strategy that the "Perfect Health Diet" and "Primal" tend to agree on. The PHD is probably a bit higher in carb since they only count startches and fruits, while Primal is all inclusive of vegetables and fiber and such.

[ChocoTaco369]

I don't think the body has a preferred fuel. I don't think the body cares what it runs on assuming it's real, whole foods. I don't think animal fat is necessarily a healthier fuel than carbohydrate from sweet potatoes. I can tell you with absolute certainty that I STRONGLY believe carbs from fruits and tubers are FAR healthier than soybean and/or canola oil! With anything, it comes down to the food source, and every study seems to show that indigenous cultures, regardless of macronutrient breakdown, seem to be relatively free of modern disease. Kitavans that eat huge amounts of carbs and very little fat and protein don't seem to be any less healthy than Inuits eating almost nothing but fat and protein with nary a vegetable in sight.

The real killers seem to be grains, sugars, legumes, PUFA-oils and the like - you know, fake frankenfood crap.

Mark seems to prefer fat for fuel because of the sedentary nature of the modern human. You know what, if you're sitting on your butt all day at your desk, you're probably better off eating a fattier/lower carb diet because it's a little more stressful to process carbs than animal-based fats. Using that logic, you may age less on a low carb diet if you're very sedentary. For someone active, I believe the opposite to be true. Active people tend to suffer and have elevated cortisol on needlessly low-carb diets. I'm a modest weight lifter, and if I go low-carb too long I feel lousy, stressed and tired. Carbs make me feel better and less stressed, so I eat them regularly and in large amounts when I get the urge. The amazing thing is we naturally seem to cry out for the fuel we want. Sedentary people generally feel tired and "crash" eating high carb diets while gym rats and athletes tend to feel like crap eating low-carb.

The real key is eating what makes YOU feel best. Pair your food to your energy levels and that's the key to success. Don't look at it in terms of macronutrients. If you're feeling sluggish, add some carbs. Reach for an apple, some berries, a banana, a sweet potato - whatever. If you're crashing after lunch at work, dial down the carbohydrate and eat fattier meat. Don't stress over health - a sweet potato is just as good as a steak in terms of health. Eat the one that makes you feel best. The only thing I stress is to make sure you're getting adequate protein. 1 pound of meat on average is ~100g of protein. IMO, most of us should be aiming for at least that, with smaller sedentary women being able to get away with the 75-100g range.

Remember - humans are omnivores. We eat meat, vegetables, fruits and tubers. It's all good. Stay away from the extremes and try to include everything in there in some quantity.

[ChocoTaco369]

The liver produces enough glucose for the body without the need of any dietary carbs through a process called Gluconeogenesis. Simply put, it coverts proteins and fatty acids into glucose, aka carbs.

This is a very dangerous stance to take.

The body does not require carbohydrate to survive. That is true - it can convert protein into glucose, and your brain can run on a mix of ketones and glucose (it can't run on pure ketones - it will always devour protein for some glucose in the absence of carbs).

Similarly, your body also doesn't need saturated fat to survive. It's plenty happy converting other sources into palmitic acid and will continue to do so - if you don't mind the inflammation.

You also don't need to take in dietary cholesterol. The body can make its own.

You won't find many people on this site saying saturated fat and dietary cholesterol are evil though, right? We praise the almighty egg and juicy steak around here. So why do we demonize the poor misunderstood carbohydrate?

Don't fall into the above trap. You don't need carbs, and you don't need saturated fat or cholesterol. However, to function in optimal health and maximize performance, you should consume all these things.

If you're happy forcing your body to devour your lean muscle mass to fuel a glucose-starved brain, that's up to you. I can tell you from experience my strength, mood and physical performance is much higher NOT needlessly starving my body of a macronutrient. Feel free to experiment on yourself.

[mike_h]

I've a few questions.

1.

there is a test you can take, its called a vo2 max test. it will tell you if your body likes carbs or healthly fat for fuel.

Do all VO2 Max tests give the energy source breakdown, or might some just tell you the overall oxygen consumption?

2. If one stayed low carb, does the body maintain a certain amount of muscle glycogen storage through glyconeogenesis, or are the muscles left almost completely "empty"?

3. Can glycogen from the liver be moved quickly (or at all) into the blood stream for muscle work in the absense of sufficient muscle glycogen?

4. Is there a good generalization about when gluconeogensis would use dietary protein, rather than muscle mass to do its thing?
Would most (gluconeogensis) occur after a protein meal and top up liver stores?

On a side note, my understanding was that "preferred fuel" means what the body will prioritize, not what it "likes" the best.
For example ethanol is burnt before carbohydrate. Technically it's "preferred" over carbs, it doesn't mean you should go on a high alcohol, low carb diet

[Neckhammer]

I've a few questions.

1.
Do all VO2 Max tests give the energy source breakdown, or might some just tell you the overall oxygen consumption? I dunno, but here is one guys tests...The interplay of exercise and ketosis You may have to read part II for the VO2 max stuff.

2. If one stayed low carb, does the body maintain a certain amount of muscle glycogen storage through glyconeogenesis, or are the muscles left almost completely "empty"? Yes, it will still prioritize to produce and refill gycogen stores.

3. Can glycogen from the liver be moved quickly (or at all) into the blood stream for muscle work in the absense of sufficient muscle glycogen? From what I gather...yes it will be mobilized when appropriate.

4. Is there a good generalization about when gluconeogensis would use dietary protein, rather than muscle mass to do its thing?
Would most (gluconeogensis) occur after a protein meal and top up liver stores? Sure...as long as you are consuming enough protein in the diet and doing some resistance training to preserve muscle mass this occurs.

On a side note, my understanding was that "preferred fuel" means what the body will prioritize, not what it "likes" the best.
For example ethanol is burnt before carbohydrate. Technically it's "preferred" over carbs, it doesn't mean you should go on a high alcohol, low carb diet
Damn the high alcohol low carb diet is my favorite one too!

[StackingPlates]

The real killers seem to be grains, sugars, legumes, and the like....

Your source for this bold statement?

[Neckhammer]

Your source for this bold statement?

What makes you feel that this is a bold statement?

[magicmerl]

Yeah, I would have thought that they were fairly accepted primal villains by now (along with PUFAs).

[Einz]

Your source for this bold statement?

Lol you're always trolling this guy, are you jealous?

He seems to have the most reasonable approach to paleo and doesn't come off as having an ego.

His stance is clear, eat foods that are whole and good for you, and quit being afraid of fruits and other carbs because the body can also use them for fuel and not just fat.

Also, the foods he mentioned are clearly not optimal and the statement was not bold at all.