Why a low carb diet is bad

Inspired by a moronic post stating that 55% of your diet should come from fats, and 35% from protein I am here to explain to you, in layman's terms, why this is a horrible idea.

Here's a breakdown of when, and at what level, your muscles are engaging in particular types of respiration:

< 65% max HR gets you a 30/70 split between burning carbs/fat
65-85% max HR gets you a 50-50 split
85-88% max HR gets you a 60-40 split (carbs/fat)
88-95% max HR gets you a 70-30 split (carbs/fat)
90-100% max HR gets you an 80-20 split (carbs/fat)
> 100% max HR gets you a >90-<10 split (carbs/fat)

What these numbers really tell us is that as workout intensity increases, our body shifts to a strict reliance upon carbohydrates. The reason is pretty straightforward, anaerobic respiration cannot use triglycerides as an energy source, whereas aerobic respiration can use carbohydrates or triglycerides.

A low carbohydrate diet will effectively put a ceiling on any exercise you want to do. Now, the most important part that gets lost in a lot of diet books and everything else is this:

When training to lose weight, they claim that you want to do so at a lower intensity, so as to maximize fat burning. What this simple idea fails to take into account, is that low intensity workouts may burn 70% fat and 30% carbs, but upping the intensity to a 50-50 balance will burn more fat.

Think of it this way: 70% of 100 burned calories is 70 calories from fat (about 8 g of fat). 50% of 160 burned calories is 80 calories from fat (about 9 g of fat).

By exercising at a higher intensity, we'll actually burn more fat (although as a lower percentage of the overall burned calories). Not only do we get these benefits, but it provides much better benefits to cardiovascular health.

Furthermore, a low carb diet has one major pitfall in terms of your exercising. No matter how you slice it, carbohydrates are an important fuel source for your body (the CNS needs carbohydrates since it can't use protein or fat as a fuel source). Your muscles will always seek to burn carbohydrates as well, and by ensuring that your muscles don't have enough, you'll put a ceiling on the workouts you are doing (you won't be able to increase intensity very high, or for a decent length of time).

Finally, a low carbohydrate diet encourages your body to engage in gluconeogensis (conversion of protein into glucose [and then into glycogen]) to fuel your CNS and your muscles. So, not only are you not exercising optimally, you're forcing your body to destroy its own muscle fiber in order to fuel the remaining fiber.

This is a huge part of the reason that so much initial weight loss is associated with low-carb diets. Muscle weighs 3x more than fat (mainly in water weight). Every gram of muscle that your body tears apart will bring with it another 2 grams of lost weight in water. It's unhealthy, unsustainable, and further inhibits your ability to exercise at a moderate-to-high intensity for a decent length of time. It's a main reason the weight loss associated with low-carb diets evaporates when those same people shift to more balanced healthier diets.

Good read.

It's not a long term nutrition plan, but you have every right to post whatever you like.

I'll continue to learn based off results and will adjust accordingly. I don't need one source to tell me what is or isn't good for me. But thank you for your concern.

By the way I just skimmed that read, but most of it seems to be associated with exercise. I acknowledge that carbs are good for exercise and necessary, especially when related to heavy workouts. The rest of the time when your body is simply fueling itself for standard body functions is another story on what is truly needed.

Again, you can feel how you like. I personally have experienced that a high carb and equivalent carb/protein nutrition program, all from good food sources, did not work well for my goals.


P.S. This is a good read I found. It's in a women's forum..but meh.

Muscle with Attitude (http://www.musclewithattitude.co m/readTopicMwa.do?id=164431 7&pageNo=0)

Big Monkey, your body (even when not exercising) will be tearing your muscle apart in order to turn it to glucose to fuel your CNS. That's why you'll see weight loss. It isn't "healthy" weight loss. You're not going to lose body fat %, and while you may lose weight, you'll regain it rapidly since you haven't trained your body, in any way that it's capable of adapting to, not to prioritize fat storage over glucose burning.

Anyway, if you're doing any sort of exercise, or even like to lead an active lifestyle, your diet is hindering your ability to maintain a moderate-to-high level of physical exertion. Period. There are no two ways about it, it's not as though you just need to adopt this diet for a long enough time and your body will magically be able to fuel your CNS with triglycerides. It is never going to happen, and you're doing nothing more than forcing your body to convert a lot of your dietary protein into glucose, and convert a lot of muscle fiber into glucose.

Seriously, go ask any physiologist or nutritionist who isn't trying to sell you something about this.

Ultra marathonners have a 2-1-1 (f/c/p) ratio apparently.
So yea..

what would be considered low carb for someone my size? 6'1 225. i generally eat about 350g carb, 250 protein, 80g fat. thats when im being good (alchy free). i also lose about 2lb a week on that diet. from what i read thats about the rate i want to lose it at but im sure ull tell me something different haha :]

Ultra marathonners have a 2-1-1 (f/c/p) ratio apparently.
So yea..

Yes, they all eat the exact same diet and it is a low carb diet. :rolleyes:

what would be considered low carb for someone my size? 6'1 225. i generally eat about 350g carb, 250 protein, 80g fat. thats when im being good (alchy free). i also lose about 2lb a week on that diet. from what i read thats about the rate i want to lose it at but im sure ull tell me something different haha :]

I honestly don't know where the line is at what's low-carb and what isn't. I know I eat a ton of carbohydrates (~65% of my calories). I know that less than that isn't a low-carb diet, but when you're talking about only getting 10% of your calories from carbs, it's definitely in that area.

So I don't really know how to help you except that you're eating too much protein (by about 100 grams), so you're probably getting a lot more calories from carbohydrates than you realize.

what would be considered low carb for someone my size? 6'1 225. i generally eat about 350g carb, 250 protein, 80g fat. thats when im being good (alchy free). i also lose about 2lb a week on that diet. from what i read thats about the rate i want to lose it at but im sure ull tell me something different haha :]

Your ratios currently come out to about:

45% C
32% P
23% F

To adjust to an anabolic type low carb diet, the grams would look something roughly like this to get the equivalent number of calories you're taking in now:

80g C = 10%
250g P = 32%
200g F = 58%

BTW, the total net carbs should hover around the 30g area while the rest should be fiber....so those weights/ratios may need to be adjusted to meet a 30g net carb goal.

That is fucking dumb. Go read the thread about how much protein you can really use if you still don't get why eating 1.2 grams of protein per lb body weight is retarded (hint: your body is turning .5 grams of protein/lb into glucose).

Yes I've read it. .6-.7 per lb of body weight is what I believe you are more comfortable with.

I don't advocate either. At the stage where I'm at...I don't think it's all that important. I'll worry about that when I get a lot closer to where I want to be.

Why you people are failing to understand with your "HIGH PROTEIN LOW CARB" diets, is that when you're eating more protein than your body can use, it is going to take most of that protein and turn it into glucose. You might as well be eating carbohydrates, because you're getting them anyway.

You get really wound up over this stuff don't you? =]

Chill man. Write a book and show the world how your way is THE ultimate way for weight loss, weight gain, weight maintenance, etc.

I'll be a test subject if you do legit research to write a paper or something. I've got plenty of weight to lose.

I don't have to write a book. Tons of educated, science based, approaches to diet and nutrition are out there.

They're not normally marketed to the "I WANT TO LOSE WEIGHT BECAUSE I AM MORBIDLY OBESE" crowd, because doing things the right way takes longer, and isn't new and/or novel, so sales would suck. Instead a bunch of crash diets that aren't "good" for the body and will give immediate "results" in the form of weight loss (but NOT fat loss) are the best selling diet books.

comments:

0) you don't mention ketosis at all. is this from not knowing what it is, or due to a disregard of its possible effect? most humans with normal metabolisms, when in a deeply carb-restricted state, will switch from a predominantly glucose-fueled metabolism to a predominantly ketone-fueled metabolism.

1) the majority of the initial weight loss on any strict low carb diet (roughly < 10% dietary carbs - varies by person) is from water loss. a large part of that water loss is from intracellular water. this is not a loss of muscle, although it may affect the performance of the muscle.

2) the numbers you've cited for macronutrient %'s during exercise, as far as i can tell, come from subjects not on a low-carb diet. i'm not sure there's any evidence to support the idea that these macronutrient profiles remain the same after long-term carbohydrate restriction.

3) under long term carbohydrate restriction the body will produce ketones (from fat) to satisfy most of its carbohydrate needs. your cns can run primarily off of ketones.

4) some recent studies suggest that the actual fat-burning associated with a high intensity exercise program vs a low intensity exercise program are the same. the difference in these studies vs older ones is that they consider the effect of exercise on metabolism well after the conclusion of the exercise. that is, high intensity exercise may result in an increase in resting fat metabolism. since most of your day is spent out of the gym, that's a very significant point. (yes, i realize this is a thread about diet - the comments were made in this thread however).

5) gluconeogenesis should only be the body's primary source of fuel in the event that carbohydrates are heavily restricted AND fat intake is not increased significantly. but on the basic point that this is bad juju, the answer is clearly 'yes'.

there is nothing fundamentally wrong with a low carb diet, particularly for people who suffer from some degree of insulin resistance. unfortunately too many people expect it to be some magic bullet that will make all of their fat go away. that ultimately comes down to hard work and discipline (sticking to the diet and exercise program is often more important than the particulars of your program), which most people aren't willing to put in.

Oh, well instead of speculating that the scientific evidence I've supplied is wrong, I suppose you could offer some scientific evidence of your own. Oh wait, it doesn't exist, that's right.

I didn't mention ketosis because it doesn't make a difference. The ketones that are produced via ketosis are intermediaries in normal aerobic metabolism, you can't use ketones to generate anaerobic energy, which is the exact point of this entire writing.

Without carbohydrates you can't perform moderate intensity exercise (50-65% max heart rate) for any appreciable amount of time. Period.

By depriving your body of carbohydrates you don't magically teach it a new way to burn ketones or triglycerides anaerobically, it is physiologically impossible.

Clearly, for anyone trying to lose weight in a healthy, exercised-based way (while accounting for diet) eating a low carb diet will hinder their ability to perform exercise at moderate intensities for appreciable amounts of time. For why that matters, refer to my mention on absolute calories burned being much more important than what percentage of fewer caloreis burned came from fat.

Instead of speculating wildly about how my data might be wrong, find some that refutes it. I would love to examine their methodologies and determine if the data I've been basing a lot of my conclusions on is wrong. Unacademic, poorly reasoned speculation that it's wrong doesn't help further the discussion in any way though.

Ptavv just got owned.

:lol:
4) some recent studies suggest that the actual fat-burning associated with a high intensity exercise program vs a low intensity exercise program are the same. the difference in these studies vs older ones is that they consider the effect of exercise on metabolism well after the conclusion of the exercise. that is, high intensity exercise may result in an increase in resting fat metabolism. since most of your day is spent out of the gym, that's a very significant point. (yes, i realize this is a thread about diet - the comments were made in this thread however).

Without carbohydrates you can't perform moderate intensity exercise (50-65% max heart rate) for any appreciable amount of time. Period.

Something doesn't equate. Either science is wrong and our body can anaerobically use ketones (:lol:), or Mad Monk is just spouting off a bunch of facts and not bothering to see how the dots connect. I personally believe the latter is true.

The fact is that the research he ballyhooes and claims I overlooked is one of the primary reasons not to use a low-carb diet. :shrug:

:popcorn:

:lol:

Something doesn't equate. Either science is wrong and our body can anaerobically use ketones (:lol:), or Mad Monk is just spouting off a bunch of facts and not bothering to see how the dots connect. I personally believe the latter is true.

The fact is that the research he ballyhooes and claims I overlooked is one of the primary reasons not to use a low-carb diet. :shrug:

actually i'll pick 'c' for this one. that particular comment had nothing to do with low-carb versus high-carb. it's from a comparison of individuals on a high intensity vs low intensity exercise regimen on similar diets.

you just assumed it was about low carb diets because you didn't read it carefully.