Is this Keto?

A very common question for those of us who eat a keto diet is “Is this [whatever] keto?”. Along with it comes comments like “you mean you can’t eat bread [or whatever]”.

It’s down to carbs

In the end, it’s as simple as the number of grams of carbohydrates. There are no hard and fast definitions of what constitutes Low Carb and what constitutes ketogenic. The technical answer is what amount of carbohydrates you can eat in a day/meal that keep you in ketosis.

But that begs the question of what constitutes being in ketosis. There’s also no accepted range of numbers or measurement methods. But the idea is that your body is using ketones for fuel. Even that is not an absolute since everyone uses some mixture of ketones and glucose. If you do an extended fast your body will generate glucose from your liver which converts fat to glucose in a process called Gluconeogenesis (GNG).

The easiest thing to measure and track are carbohydrates using a scale and an app like Cronometer which can show you the total number of carbs in your day.

Measuring Ketones

Ketones can be tested by three methods; blood, urine and breath. Each of these tests measure chemicals produced as a byproduct of ketosis. There’s some correlation between these three measurements but even that is not absolute.

Nutritional Ketosis Measures Blood Ketones

A widely accepted method is to use blood ketones and measure them against a standard. Except that there is no standard. Often cited is Stephen Phinney’s definition of “nutritional ketosis” illustrated below:

This says that blood ketones in the range of 0.5 to 3.0 mmol are optimal for brain and muscles.

Is this Food Keto?

Using this definition any food which you eat over a meal/day that drops your blood ketones below 0.5 mmol is not keto. But there’s no easy mapping of how many carbohydrates it takes to push someone to below that number. A commonly asserted amount is 20 grams of carbohydrates per day will take a person out of nutritional ketosis. For most people this number will be adequate. For others it may be too high and for others it may be too low.

The Only Way to Know is to Measure

The only way to know for sure is to measure the effect of a particular food or activity on your ketone levels. And testing isn’t cheap at around $5 a test strip. I’ve used the Precision Xtra meter for my measurements but I never actually mapped carb amounts to ketone levels. I mostly tracked the ketone levels vs days of fasting.

Cheaper Way to Measure

A cheaper way to measure is urine test strips. They are around $5 for 50 strips. You pee on a strip and compare the color of the strip to a scale. They work well for most people (at least at the beginning) but are affected by urine concentrations (which is a function of your level of hydration). They are also slow to react to diet changes. They can indicate what your level of ketosis was hours ago.

Another Expensive Way to Measure

I also bought a breath ketone measurement device, the ketonix. It is fairly expensive but can be reused.

The trouble is there’s a messy mapping from breath to blood ketones. Here’s the scatter diagram from breath to blood ketones with the best fit curce. Going up from 0.5 mMol to the line shows that that’s something like 2.0 PPM.

The ketonix has a USB interface and the data can be downloaded to your computer. Here’s a screen shot of one capture showing the level at 5.4 ppm which would be around 1 mMol.


In the end, the best way to be in ketosis is to eat a very limited amount of carbohydrates such as less than 20 grams a day.


Ketone Measurement in Pee Strips

Turns out there’s actual scientific evidence of urine ketone differences between individuals on a low carb diet. And the levels are not a measure of the body’s ability to make use of ketone bodies as some claim.

The evidence comes in the form of a unique scientific experiment done in 1930 on Vilhjalmur Stefansson. Stefansson was an arctic explorer who lived in the arctic for many years and had become accustomed to eating a diet consisting solely of meat (My Life with the Eskimo). The conventional wisdom of the day was that a low carbohydrate, meat-only diet was unhealthy.  A scientific experiment was created to reproduce his meat only diet under metabolic ward conditions. He consisted on the diet for over a year. This was early enough that the conditions of ketosis had not been extensively studied but recent enough that equipment to measure ketones and other blood contents were available.

The experiment is documented (Prolonged Meat Diets with a Study of Kidney Function and Ketosis). One of the many interesting points is the measurement of urine ketone levels. One of the participants had an increase in measured ketones (in urine) and the level stayed high. The other participant on the same diet had a drop in levels over time.

This validates the observation that some individuals on a ketogenic diet continue to have measurable urine ketone levels and others have much lower levels.

Keto in One Graphic


Hit that number. Or go higher.


Eat less if you want. Don’t eat more.


More fat in your diet is less fat off your body. Less fat from your food is more fat off your body.


Self explanatory.


Track your macros. Everything you eat. Every bite. No need to cheat yourself or lie to yourself. Only way to know where you really are at. Especially when changing your macros.

If you don’t know your macros try the ketogains calculator.

If you want max fat loss, try my calculator but you may hate the recommendations.



Types of Exercise and Glycogen

I have been trying to tease out the limits of low carb performance. Here is a key paper (Metabolism. 1983 Aug;32(8):769-76. The human metabolic response to chronic ketosis without caloric restriction: preservation of submaximal exercise capability with reduced carbohydrate oxidation. Phinney SD, Bistrian BR, Evans WJ, Gervino E, Blackburn GL).  Buried within the paper is:

In agreement with this were a three-fold drop in glucose oxidation (from 15.1 to 5.1 mg/kg/min, P less than 0.05) and a four-fold reduction in muscle glycogen use (0.61 to 0.13 mmol/kg/min, P less than 0.01).

This seems buried because of the units used. Another site (September 13, 2017. Why Am I Getting Low Ketone Readings on a Ketogenic Diet? By Mark Sisson) translates these units as:

During the high-carb arm, the group began the workout with 150 grams of glycogen and ended it with 50 grams. While eating ketogenic, the group began the workout with 75 grams and also ended it with 50 grams.

The time of this test was approx 150 minutes.


Very-Low-Carbohydrate Diet Studies

This will be a growing list of Very-Low-Carbohydrate Diet Studies (and related subjects).


The Name “ketogenic diet”

There’s a problem with the name “ketogenic diet.” The problem lays in the origin of the term and the appropriation of the term as a weight-loss diet term. Much of the earlier scientific use of the term in medical literature refers to the origin of the term. More specifically, originally the “ketogenic diet” referred to

…a high-fat, adequate-protein, low-carbohydrate diet that in medicine is used primarily to treat difficult-to-control (refractory) epilepsy in children (Wikipedia)

The ketogenic diet was widely used to treat seizures until the advent of anti-seizure medications. For a large number of patients the medications removed the symptoms and they were able to return to the Standard American Diet. But for some portion (maybe 20-30%) the medications didn’t work and the diet was the only thing which provided relief.

The medical uses of the ketogenic diet had been high fat and included just enough protein to spare muscle mass. This was done in the medical ketogenic use to minimize blood sugar increases from protein (there’s some blood sugar rises from dietary protein although much less than from dietary carbohydrates). This was probably appropriate and necessary for seizure patients who needed to fuel as much of the brain as possible using ketones as the fuel source. Also, the main patients were children who needed a higher fat diet for growth.

There were many medicals studies done of the effects of the ketogenic diet in the seizure community and the diet was generally well tolerated and effective. It also had the side effect of dropping body weight in those who had the diet.

Along came Dr Atkins who popularized the Banting Diet (from earlier years). The major emphasis there was low carbohydrate levels. Aktins started people at 20g of carbs for a couple of weeks (called induction) and later allowed for some increases in carbohydrate levels.

Since there are only three macronutrients reducing carbohydrates meant that protein and/or fat would need to be increased. The medical community used ketogenic (low levels of protein) and higher levels of fat. The Low Carb community (Atkins and such) had higher levels of protein and lower levels of fat.

That set us up for the current state of affairs. The term ketogenic has been taken in two different directions. For some, chasing ketones has become the goal. For others, fat loss is the goal.

I don’t care what my ketone levels are.
I do care about what percent body fat I have.

My proposal is to give back the term ketogenic to the medical community for use with seizure patients. Stick with Low Carb or some other term. Come to some agreement about what macros are allowed and not toss people out of Low Carb groups for having higher protein or lower fat.

Protein Sparing Modified Fast Calculator

I put together the previous formulas into one single webpage, the Protein Sparing Modified Fast Calculator. I’ve put my own current numbers into the calculator. Just hit the “Calculate” button to see my numbers. Feel free to try it out with your own numbers and see if it helps you figure out any of this. I don’t see the numbers you enter nor are they stored in any database. All of the calculations are done on your phone web browser or Internet browser (Firefox and Chrome works but Internet Explorer doesn’t).

If you find any errors, please let me know. I tried it with my own numbers and they make sense but I didn’t have a woman’s secret numbers to check.

Here’s a decent introduction to the Protein Sparing Modified Fast (PSMF). I only take exception to one point which is the question of how long you can do a PSMF. They say you can’t do it for an extended period of time. If you continually re-calculate your numbers you should be able to fine tune for maintenance levels. This calculator makes that re-calculation relatively easy. Here’s the results I got for my numbers.

Your Scale and Metabolism Numbers

Current Weight: 199.8 lbs
Goal Weight: 171.3 lbs
Lbs from Goal Weight at start: 28.5 lbs
Body Fat at start: 25.4%, 50.8 lbs
Lean Body Mass (LBM): 149.0 lbs
Basal Metabolic Rate (BMR): 1818.0 cal/day
Initial Total Daily Energy Expenditure (TDEE): 2500 cal/day
Initial Maximum Fat Loss on Protein Sparing Modified Fast: 0.45 lbs of body fat per day


Protein Sparing Modified Fast (PSMF) Dietary Macros (per day)

It is very important on the PSMF that you eat at least the macros listed here. If you go below these numbers you risk lowering your metabolism and you actually can’t lose body fat any faster. Attempting to be just above the numbers is OK.

Protein: 119.2 g (476.8 cals)
Carbs: 20 g (80 cals)
Fat: 40.9 g (367.7 cals)
Your total Dietary Calories are 924.4 cals for maximum fat loss.

If you consume 216 g (1943 calories) of fat you will stay at your current weight.At your goal weight you will be able to consume 119.2 grams of Protein, 20 grams of Carbs, and 176.3 grams of Fat.


Can You Fast?

One important question to ask when considering extended fasting is whether or not you have sufficient body fat to fast.

You currently use 2500 cal/day. You have 1575 calories per day available from your body fat for maintenance. You have less calories available from body fat than your daily requirements and may not be able to fast. If you fast, your body may drop your base metabolism, energy expenditures or may consume protein stores. You will be -924 calories short per day

The thermic effect of food contributes somewhere from 5-20% of your current TDEE number so if you are fasting that can reduce your TDEE. Reducing your TDEE by 10% would result in you using 2250 calories per day. Calculating in a 10% Thermic Effect of food still leaves you in a caloric deficit during fasting. The Protein Sparing Modified fast solves this issue by providing the calories needed for the deficit.

How Much Muscle Can You Gain?

The Maximum Lean Body Mass that you can carry on your frame is 186.5 lbs at your goal of: 15.0% Body Fat. That would be a weight of 214.5 lbs.


Use this information at your own risk and with the advice of your medical professional. We are not doctors nor do we pretend to be one on the Internet. We do not take responsibility for errors in these calculations. We do not guarantee that these numbers will work for people at the extremes of the ranges. If you discover an error in calculation, please let us know through email: keto at land-boards dot com.