I've been doing a very low carb ketogenic diet the past couple weeks and revisiting some of the nutritional theory that floats around the internet under the name of diet advice.
For many years I have used nutritional software and a food scale to track and log my food intake when I diet, so I have a very good idea of what I'm eating. But recently I've gotten curious about the impact of macronutrient balance: how much of a difference it makes when we change the proportions of protein, carbohydrate and fat that total up to a given caloric intake.
When we cut carbs, we know we have to raise our protein intake high enough to provide the raw material from which the liver can synthesize the glucose it needs to run the brain--the only organ that requires some glucose to keep running. At the outset of a ketogenic diet the brain requires about 100 grams of protein.
We also know--though many supposedly trained nutritionists do not--that after three weeks on a ketogenic diet, the brain's requirements for glucose drop significantly--to about 40 grams a day--as it ramps up to run on ketones instead.
(This last phenomenon is why children with certain kinds of epilepsy are able to eat extremely low carbohydrate diets for years at a time and heal their brains.)
Our bodies also need dietary protein to repair our muscles. There are formulas we can use to calculate how much extra protein we need for this function.
If we eat enough protein, our bodies will not cannibalize lean muscle as we diet. So getting adequate protein is essential to healthy dieting. But there are limits to how much protein we should eat: too much protein will not only stall weight loss but will produce the unpleasant "diet breath" that many dieters erroneously attribute to ketones. In addition, excess protein can turn into glucose and raise blood sugar. So our goal when dieting should be to eat only as much protein as we actually need.
Once we know how much protein and carbohydrate we are going to be eating, the next question we need to ask is how many calories we want to eat. The traditional diet advice is to calculate your resting metabolic rate (BMR) --the amount of energy you use just breathing, digesting, and pushing blood around your body, and add to this the amount of calories burned by activity.
Many formulas exist to estimate the BMR, though they work best for large populations, not individuals. I reviewed the research that tested these formulas against actual measured BMRs, and it looks like the formulas that do the best job at estimating BMR in real people are the Mifflin-St Jeor formulas.
It turns out that the Harris-Benedict equations that many web sites use in their calculators were developed in the early 1900s and err by 18% when tested in the lab. They often overestimate calories burned and dieters who use them to set caloric goals may end up overeating.
Once we know how many calories we are supposedly burning, we can, in theory, lose a pound a week by eating 500 calories less than we are burning. This allows us to set a calorie goal.
Once we know how many calories we want to eat, we can calculate how much fat we can add to our previously computed protein and carbohydrate intake to come up with a final macronutrient prescription.
I've put together a calculator that will compute your own macronutrient prescription using the principles just outline and I'm inviting you to test it out.
The calculator is only designed to prescribe macronutrients to people on a ketogenic low carbohydrate diet, defined arbitrarily as one that does not exceed 80 grams of carbohydrate a day. It is only for adult use and should not be used by people older than 75 whose BMR is not calculated properly by the Mifflin-St Jeor formula.
It prescribes a nutrient breakdown for both maintaining your weight and for losing weight. However, no matter what your metabolic needs. It will not prescribe a diet of under 1100 calories a day out of a belief that eating below that level may unduly slow our metabolisms.
I put this calculator forth understanding that many people eating very low carb diets find it possible to eat more calories than nutrition formulas predict and still lose weight or maintain weight. Turn to this calculator if you are stalled.
This is a beta version. I'd be very interested in hearing from those of you who track your nutrients how well the calculator's prescriptions match your own experience with successful weight loss.
For those of you who are stalling on your diets, I'd be very interested in hearing whether using its prescriptions can help you break your stall.
Here's the link to the calculator:
Calculate Your Nutrient Balance on A Ketogenic Low Carbohydrate Diet
Please post your feedback about the calculator in the comment section of this post.
Thanks!
January 13, 2009
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10 comments:
These calculators always leave me going, "Uh, seriously?" Having started going to the gym a few times a week, and given that I don't really eat lunch beyond a whey protein drink (I do have a good eggs and bacon breakfast, mind you, or switch the two meals if scheduling requires it.) That leaves me eating, I dunno, a pound of beef for dinner and still being 69g fat short of what it suggested. Of course, that's 600 or so calories lower without being anywhere near the cutoff... hmm. :)
(Indeed, it's still about 2000 calories. I'm a big guy.)
I always feel skeptical at times like that, but at least it's easy to remember. Normal eggs and bacon for a meal, whey protein drink for a meal, pound of meat for a meal. :) A few low carb and essentially therefore macronutrient free veggies with it and...
Your calculator tells me to lose safely, eat 1,665 calories.
"You have decided to eat 50 grams of carbohydrate a day. To avoid loss of lean muscle mass you must eat 146 grams of high quality protein each day. Round out your diet with 98 grams of fat."
The site that I am using to log my daily intake set mine like this based on me setting my carb intake at 15% (56g) and my doc's recommendation of 1500 calories:
1500 calories
56g carbs
150g protein
75g fat
I struggle to get my calories in and I've yet to reach the protein requirements. I usually do good on fat since I use olive oil, eat nuts and avocados. I just decided today to look into drinking a lower carb, lower fat protein shake at mealtimes. EAS has a light shake that will up my calories and protein without hurting me too much on the fat/carb intake. As I understand it, if I don't eat enough calories, that is enough to stall weight loss, correct?
Oh, and though I am new to commenting on your blog, I've been reading you for quite a while here and at other sites :)
Careful with the EAS products. Many of the "low carb" ones are filled with things that will raise blood sugar, often a lot. Glycerine turns to glucose in the liver if you are low carbing. Maltitol is 1/2 sugar.
I personally find I do a lot better on my diet if I avoid all the frankenfood protein powders. They aren't real food and who knows how nutritionally effective they really are.
Meat, cheese, eggs work a lot better.
Looks useful. I think it would help if you'd convert fat, as well as protein, into ounces.
Ok, thanks for that info, I wasn't aware of that. But, if I do meat, egg and cheese, I'm afraid my fat allowance will be through the roof.
Thanks for this; I have been wrestling with this particular issue, and in fact posted about it the same day on my food diary blog, http://sara.blogspot.com.
One thing I'm still trying to figure out is the upper bounds -- I've picked up on some of the consequences of too much protein, but I can't get a real handle on how much is too much. Is it a 50% exceedence of requirements, is it a doubling, does it matter if you exceed this once in a while as long as you're normally close to goal? If you have any resources that would help quantify this, I'd love to see them.
Sara,
I would stick as closely to the recommendations that my calculator gives as possible. It is already estimating up about 10%.
One easy way to tell if you are overeating protein is if you develop bad breath. This is often blamed on ketones, but may be due to the ammonia compounds released in metabolising protein.
Also, urine with a lot of ammonia may irritate your tissues, another sign of too much protein.
Like all the suggestions I make, these are mostly relevant if you are stalled, if you are losing weight happily and feel good, then no need to obsess. For me the protein issue can be a staller, though.
I just realized that the site that I am using to log my food, etc. is also using the Mifflin-St Jeor formulas, which explains why the numbers were so close! :)
The weight loss suggestions for the metabolic advantage choice are bang on what works for me, but the maintenance calories are higher; it's suggesting 2000 calories, I do better at 1800. I also do quite a lot of activity; if I go for "light exercise" instead, it thinks I could maintain on 1900 calories. Interesting! Good job I do karate for fun, not weight loss : )
Nicky,
The maintenance calories will only work if you are still eating at a ketogenic level, which would probably be under 65g for most of us ladies.
Also, I don't think the exercise activity factors are correct. They are commonly used, but I think they overestimate the impact of exercise. Analyzing my data I saw them match some months, but other months with the same intake I would gain a bit. Maybe muscle? But whatever it is, I'd err on the side of not counting on much exercise calorie burning.
This article is a Must Read for anyone interested in calories and exercise:
Putting very Little Weight in Calorie Counting Methods.
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