Ketosis/Lipolysis vs. Ketoacidosis

matthew's picture

Got a question regarding the metabolic processes of ketosis/lipolysis vs. ketoacidosis on a forum yesterday. Thought I'd post my response here, since it's really a frequently-asked-question by people who are modestly familiar with diabetes and confused by the similarity of terms.

1. In a low carb diet consisting of less than the required carbohydrates the body enters Ketosis. What in a normal healthy person prevents this from developing into a state of ketoacidosis?

Corrections to your question:
1. There is not necessarily such a thing as "required carbohydrates". Your body can manufacture all the glucosal needs of your tissues via gluconeogenesis, or the process of converting protein into glucose. Also, some tissues which prefer carbohydrate metabolism to ketone metabolism -- like your brain -- will eventually convert to at least partial ketone metabolism. That said, some carbohydrate is necessary for the phytonutrients (plant-only nutrients) required by your body. Humans are omnivores, after all.

2. Ketosis/lipolysis and ketoacidosis are two completely different metabolic processes which share only the same by-product and unfortunately similar names. The state of ketoacidosis is due to wildly high blood sugar and a failed pancreas, whereas ketosis is the result of the body manufacturing glucose to prevent low blood sugar.

I would restate your question: "In a low-carb diet the body enters ketosis/lipolysis for extended periods. What is the difference between ketosis/lipolysis and ketoacidosis?"

So to be clear: you simply cannot get into a state of ketoacidosis by eating low-carb. In fact, even Type 1 and Type 2 diabetics cannot enter into a ketoacidic state by eating low-carb. You can only get into that state by consuming too much high-glycemic food and producing little to no insulin to stabilize this out-of-control-high blood sugar (or by being so insulin-resistant that the insulin does no good... and low-carb eating fixes insulin resistance).

Viewed in that light, the question of how a healthy person prevents ketoacidosis while low-carbing is a non-sequitur. The two metabolic pathways have nothing to do with each other except the by-product of possible ketones in the urine. It's much like asking how much gasoline would a person have to drink to create a carbon dioxide profile similar to that of a motorcycle. Humans don't contain internal combustion engines even though we produce carbon dioxide -- like a motorcycle does -- as a by-product of oxygen consumption.

2. Is there or is there not a threshold of carbohydrate intake that will essentially pull you out of Ketosis? Or in other words if you have entered a state of ketosis but then gradually increase carbohydrates after the switch is made to a suggested amount that is below the norm of suggestive carb intake, what prevents your body from coming out of ketosis and utilizing the conversion of carbs into glucose for energy?

This is a common low-carb fallacy. You aren't "kicked out" of ketosis by breaking through a certain magic number, nor are you kicked into ketosis by the same. Your body has a sliding-scale of fat-burning metabolism dictated largely by your insulin and cortisol levels. However, there is a certain level of carbohydrate and protein consumption at which the level of ketone in your blood is low enough that your kidneys no longer filter ketones out. The point at which my Ketostix stop turning purple is around 40-50g of carbohydrate per day.

So let's distinguish here: Yes, there's a certain carbohydrate (and protein) consumption level at which your body no longer excretes a measurable amount of ketones into your urine. If you are in lipolysis -- losing fat -- your body is always secreting some level of ketones into your bloodstream. This is why the Ketostix are a nice morale-booster, but little else. The real clue is your shrinking waistline, reduced body-fat percentage, and more-defined musculature to allow you to track your level of ketosis/lipolysis.

Even the low-fat dieters enter ketosis/lipolysis. They just enter it while they are sleeping, or several hours after each meal, while we low-carbers are in it all the time but might be metabolizing dietary fat for ketones and protein for glucose rather than carbohydrates for glucose. We're not mobilizing body fat all the time, either, but we are always mobilizing fat of some sort.

I am just trying to understand, to the most of my ability, what exactly occurs during the process and how it is really balanced.

The take away message here:
1. Ketoacidosis and ketosis/lipolysis are two completely different metabolic processes on opposite ends of the dietary spectrum. A healthy person cannot have a ketoacidic bloodstream while consuming a low-carb diet.
2. Whether or not you are in ketosis/lipolysis is not a black-and-white game. It is a sliding scale of function, dictated by your own dietary needs, and if you are losing fat you can be certain your body is producing and using ketones for energy. Measurement of ketones in urine, however, tends to be an all-or-nothing proposition as your kidneys filter out excess ketones.

Note none of this applies if you are in acute renal failure; you must carefully manage your protein -- and thus urea -- quantities if you don't want to be hooked up to the dialysis machine 24/7. Also if you are hospitalized due to extreme insulin resistance, or near death due to multiple organ failure, this doesn't necessarily apply.

As usual, I'm not a doctor, YMMV, etc. However, I read WAY too many science books for my own good. Recommended reading: "Good Calories, Bad Calories". It describes these metabolic processes in excruciating detail.

Matthew P. Barnson