May 7, 2012

Check out my new diet calculator--completely revised and updated

I spent some time last week rewriting the nutrition calculator that used to tell people how much protein they should be eating on a ketogenic low carb diet. Now it isn't restricted to ketogenic diets and provides several other new features. You'll find the calculator at:

I've revised it to do the following:

  • Calculate caloric needs based on either total body weight or lean body mass by providing the ability to enter body fat percentage. This gives a much more accurate result for heavy people whose extra weight is largely contributed by fat which doesn't require much protein to sustain it.
  • Provide the ability to specify how much fat-related weight you'd like to lose each week. The calculator will also flag unrealistic weight loss goals including those that would require cutting protein down to unhealthy levels.
  • Allow any carbohydrate intake level to be entered. If the carbohydrates entered exceed 120 grams a day, the calculator changes its recommendation of fat and protein levels to match the nutrient intakes that appear to be the healthiest, based on the research I reviewed for my new book.

The calculator continues to account for the additional protein required by people on very low carb, ketogenic diets. But it also makes it clear that as carbs rise and the diet continues past the first few weeks when the body adjusts to the ketogenic state many people will need far less protein than they might think. Cutting out that excess protein is often the easiest way to break a low carb weight loss stall--and to eliminate diet-associated dragon breath.

I found that when I calculated my own caloric needs by entering my body fat percentage as measured by my Tanita scale first thing in the morning, the calorie and protein levels that the calculator came up with matched exactly the caloric intake and protein levels my food logging had shown to lead to continuing weight loss and, when I reached goal, successful maintenance.

This had not been the case when I calculated my nutritional needs using other online calculators that asked only for my total body weight. Most interestingly, entering my body fat percentage along with my total body weight into the new calculator provided a new daily calorie level that was a couple hundred calories higher than that provided by other calculators.

This eliminated the caloric difference that in the past I had attributed to the "metabolic advantage" of a ketogenic diet. It turns out that the only reason I could lose weight on a ketogenic diet at a higher caloric intake than suggested by the formulas beloved by nutritionists is that I have more lean body mass for my size than their whole-body based formulas assumed so I burn more calories.

This is in line with much of what I learned doing my research. I'd love to hear from you as to how the calculator's estimates match your own experience maintaining your current weight or achieving weight loss. Post in the comments section of this post and we'll keep the discussion going there.


Mary B said...

Jenny, I plugged in my info: 68 inches, 126 lbs., age 50, light exercise, body fat 21%, eating 130 grams of carbs, not trying to lose weight, and the results said recommended protein intake should be 139 grams which would be supplied by 23 ounces or 644 grams of high protein food and only 62 grams of fat. Isn't that way too much protein? And what's with the 139 vs. 644 grams? I eat a lot more fat than 62 grams as I'm sort of following the Perfect Health Diet. I haven't got your book yet so I don't know what research says to limit fat to 30% of total calories if you're eating over 100 grams of carbs a day. Seems like too much protein and not enough fat to me.

Unknown said...
This comment has been removed by a blog administrator.
Jenny said...

Several of the research studies I reviewed when writing my new book found that as carbs rose over 110 g a day and certainly by the time they approached 150 g a day if people did not cut their fat down to no more than 30% of calories their cholesterol profile switched to the kind that suggests small atherogenic, rather than large, healthy LDL particles, which is not a healthy profile. Many people eating high fat intakes at that carb intake level ended up regaining lost weight at a swift rate. The Zone dieters who were eating 30% fat and 30% protein did far better when eating at that carb range, so I have adjusted my recommendations to reflect this.

Since you are slim it might not be the issue for you that it would be for someone struggling to maintain a weight loss, but it's worth thinking about.

Jenny said...

Unknown: Of course you were right! That's what I get for going through the new comments before I've had a chance to drink my morning coffee!

I've deleted the post where I screwed up and replaced it with a corrected one.

Unknown said...

It looks like the calculator, by limiting the fat to 30%, is making up the rest of the neccessary calories with protein. I would think it would be really hard to eat 139g of protein day after day, you'd feel stuffed. Maybe protein shakes would be required. I also wonder if it would cause weight gain.
I always thought that the way to go would be to fix carb and protein levels and add fat to make up the calories. Then if you gain or lose, adjust the balance between fat and protein to stabilize weight.
I can see if someone was eating 250+g carb, low fat (30%) might be a good idea, but 130g carb is a lot less than most people in the different studies usually eat. I think 40% fat is medium fat.
I would look at my tgl/HDL ratio before I worried about switching to low fat.
How does rounding during calculations equal 200 calories difference?

Jenny said...

In theory what you suggest might work. In practice, based on the studies, and on what I've observed in peers, once people's intake rises towards 150 g a day they seem to go out of control with their eating very easily.

And there is also the issue that people rarely count carbs accurately, so many people who think they are eating 120 g a day are really eating 150 or more. Portion size explains a lot of it--how many people weigh their portions? As does hidden carbs.

Since this is a low carb diet calculator, the point is to make people aware that if they are eating more than 120 g a day they are no longer eating the kind of low carb diet described in the low carb diet books and that they really should think carefully about fat intake.

I'd be interested in hearing from people eating 150 g a day with higher fat intakes as to what happened to their blood pressure, cholesterol ratios and triglycerides. And of course, their post-meal blood sugars.

Unknown said...

Anybody eating more than 100g carb will have trouble following the calculated amounts. I plugged in Mary B's numbers and the calorie count was 200 off, rather than less than 10 calories or so from rounding error. I still don't believe anyone her size would be able to eat 139g protein every day for very long. I think it would be pushing it to try to eat 1g protein per pound of body weight without a lot of weight training and trying to build muscle.
If the calculator was accurate for carbs over 100, it would be telling her to eat 193g protein.
[(130+139)*4]+(62*9)=1634 but the calculator says 1851 calories.
To use 130g carb and 62g fat in the calculation:
[1851-(62*9)-(130*4)]/4 = 193.25g protein.
You used to warn people about eating too much protein on a low carb diet.

Jenny said...

The calculator works just the way it used to as far as recommending protein and fat up to 120 g a day After that it switches modes.

In the past, I didn't let people use the calculator to calculate intakes if they were eating more than 100 grams of carbs a day, because the fat calculation was based on the assumption they were eating a ketogenic diet.

But once they eat over 120 g of carbs a day, the calculator limits protein and fat to 30% of total calories. And yes, that does cause issues because the carbs aren't quite high enough to make up the extra calories.

But I do this on purpose, because the research I've reviewed suggests that intermediate carb range with high fat isn't a healthy range to eat in.

jkim said...

The calculator lists protein as 6 grams per ounce. Is that cooked or uncooked weight? And if cheese is a countable protein, is Greek yogurt? What about whey protein or soy products? Shouldn't they also be included in the protein count?

I find that when I eat less protein my glucose readings are lower. But I also need to gain weight and i think a little more protein helps there, too.

Jenny said...


That's a rough estimate. You'd need to look up the specific food you were considering using nutritional software to find out exactly how much protein it contains at a given portion size. No one can be exact here because we aren't eating the same steak, or cheese, or yogurt.

If you look on the label of the Greek Yogurt you'll see exactly how many grams of protein are in the container. It varies from brand to brand.

jkim said...

I always read the labels, and I include their protein grams in my daily count. But at the end of the day, my total is 60 or more grams, 1/3 more than the calculator says I should eat.

jkim said...

Oops, make that 50% more than the calculator says. Math was never my strong suit.

Jenny said...


60 grams of protein sounds quite low unless you are very slim. If you aren't having a problem with stalled weight loss or bad breath, there's no problem with it.

jkim said...

Yes, I'm quite slim--5'5" and 100 lbs, which is why I'm trying to gain weight. But of course my slimness doesn't let me gain by eating carbs--not that i'd do that anyway.

It's a crazy catch-22.

I know I should probably be eating lots more good fat, but I'm nervous about upping the fat too much until I have my cholesterol check later this month.

Thanks for all the work you put into your blog, Jenny. It's educated me a lot.

Jenny said...


The story on cholesterol is that as long as your carbs are very low, you can eat healthy fats safely. 68% fat works with an intake that puts you into a ketogenic state. Since you are small, that might be a very low carb intake. The problems arise as carbs approach 40% of daily caloric intake. At that point you don't want to be eating a lot of fat and would have to fill out your caloric intake with protein.