In Part 1 of this four part series, we talked about how to kick start a LCHF lifestyle; what to eat and what not to eat. See “Getting started on LCHF – Part 1: Clean out day”.

In Part 2 we will look at how best to navigate the (sometimes difficult but hopefully brief) fat adaptation phase. Becoming fat adapted, or a fat burning machine as I call it, is necessary to see the full benefits of a low carb high fat whole food diet.

What is “fat adapted”?

When you have settled into a low carb high fat diet for a while, most people will describe a switch over in the way they access and use carbs and fat as fuel in their body.  We call this being “fat adapted” or, more technically correct, becoming “metabolically flexible”.

This is the ability to switch in and out of nutritional ketosis depending on whether carbohydrate is available or not. A metabolically flexible individual can be a carb burner OR a fat burner.  Many, including me, would describe this as the normal or default physiological state for humans. Mark Sisson wrote a nice post about this a while back.

I would say the major benefits are:

• Burning less carbohydrate and more fat, both at rest and during moderate intensity exercise.  Less glycolysis means less oxidative stress, reactive oxygen species, and less glycated end products. That’s all good and means a better immune system and better health.  It also means that fat is more easily burned as the primary fuel source.
• Missing meals and occasional opportunistic fasting is easy to do.  If you miss a meal for whatever reason, or they serve up inedible processed rubbish at a function you’re at, as a fat adapted individual you won’t miss a beat.
• You will be burning fat as a primary fuel source because insulin is kept lower across the day. The appetite and weight regulation system, through the hypothalamus and leptin-insulin interaction, will work as it should.  It will now be easier to maintain a homeostatic weight.  You should feel more energetic because the vagal nerve isn’t down regulated to conserve energy, as it is when you are leptin resistant.
• There is no longer the “glucose cliff” which most carb dependent people fall off each day. I think you know what I am talking about – it’s the  time in the day when the brain is saying “feed me or else”.  This just disappears and you end up with sustained energy from fat and good mental acuity the whole day.  For me this is massive and the major benefit of keto-adaptation.
• You will probably sleep better.
• There is an all round sense of calmness, at least for me, which isn’t there when I am going nuts on the carbs!

How to get fat adapted

Although the benefits of a LCHF lifestyle can often be seen in a matter of days, it is only once your body relearns how to use fat for fuel that you will start to experience effortless weight management, stable energy levels and for active individuals, the ability to perform and recover more efficiently and effectively.

First step is to start a Low Carb High Fat diet (see Part 1 of this series). Stick at it for 3-4 weeks and for many, that will be all it takes. BUT, there are several very important nuances which can either stop you from getting there, put you in a “feel like crap” metabolic grey zone, or have more serious issues. Here’s what to look out for and how to avoid them.

1. Quickly moving through the adaptation phase

It’s almost certain that you will get some (or all) of these symptoms if you have been on a moderate to high carb diet and you switch over to a low carb high fat whole food diet.

• Dizziness
• Light headedness
• Brain fog
• Lack of energy
• Craving for sweet stuff because of sugar/carb addiction withdrawal

This is normal as your brain has been used to getting 100% of its fuel from glucose.  When there is no longer enough glucose to do this, the body will have to supply fuel from ketone bodies – notably beta-hydroxybutarate (BHB). For most people this isn’t a simple switch, as the machinery for doing so will require some biochemical re-orchestration. This basic physiology appears to be lost on most doctors and dieticians worldwide.  Yet it is probably the default energy system humans have run on for millennia.

My suggestion is to plan for this in advance.  If you have a job that requires actual thinking and attention then best start on a Thursday or Friday or while you’re on holiday. In my experience, it takes a couple of days to deplete the body’s glycogen reserves. Then you can have the ‘down’ couple of days over the weekend and hopefully most of the symptoms will be gone by the start of the next week.

It is critical during this phase that when you crave sweet things or carbs, you don’t succumb!

• Eat enough salt. I think this is a real problem for people.  As the body adjusts, sodium tends to be dumped by the body to preserve the sodium-potassium balance in the body. You may also be eating way less processed food and thus less salt as well.  Low salt can result in hypotension (low blood pressure) and cramps, dizziness, lack of energy and so on.  I often have people add quite a lot of extra salt in the adaptation phase – up to 5 g a day extra.  That’s a lot.
• If in doubt, eat more fat.  Don’t regard the adaptation phase as a weight loss phase.  You may end up losing weight, but the key is to make the metabolic switch.
• MCTs may help.  Medium chain triglycerides, like Lauric acid (found in coconut oil), may help in alleviating symptoms. MCTs can be used by the brain directly as a fuel source.  So extra MCTs may help provide a second temporary fuel source to the brain as you adapt. We do need more evidence about this though which is why we have doctoral student Cliff Harvey, a long time keto-diet naturopath and nutrition guru, looking into exactly this.

2. Avoiding the grey zone – low carb limbo is a horrible place to be

• Watch your carbs. Eating too many carbs will mean that you don’t quite deplete the brain of glucose enough for it to have to reset its fuel supply. This will most probably be the biggest stumbling block for most people. You can end up in a grey zone where you rarely have enough glucose to run the system, but you haven’t depleted it enough to stimulate ketone production and use. It hurts and it’s no fun and it’s unnecessary. Most people, depending on activity level, will initially need to go below about 50 g carbs a day.  That’s not much and carbs do hide everywhere, especially in processed food.
• Watch your protein too! When you eat protein in excess of your daily needs – more than 0.8-1.2 g kg-1 body weight (about a deck of cards size of protein each of three meals) – then that extra protein will be converted to glucose (carbs) by the liver through gluconeogenesis. This is the hardest part by far in switching to this sort of eating plan.
• Know what you’re eating. You have to have some way of learning how much carbs, protein and fat are in the various foods that you eat. The easiest way, thank goodness for technology, is a mobile app. In Australia and NZ the best is Easy Diet Diary – simply because it has the food database from both countries.  Don’t worry about the calories, but look at the grams of protein, carbs and fat you are eating each day.  I would have around 30-40 g of carbs, 120 g protein, and the rest, usually 180-200 g, would be fat (46 year old, 84 kg male with moderate activity level).

3. Measuring success

If you are successful, you will lose the carb and sugar cravings, develop a completely regulated appetite, and become a fat burning machine. That’s great, but are there ways of quantifying success beyond how you feel?  Yes, here’s how.

• RQ – we use this in our lab – we use online gas analysis to understand the ratio of expired oxygen and carbon dioxide to work out the respiratory quotient (RQ).  RQ 0.7 = 100% fat burning. RQ 1.0 = 100% carb burning.
• Keto sticks – these measure urine acetone. I don’t particularly like this method as it’s not reliable and doesn’t measure BHB.
• Blood ketones – this is really easy and quite cheap. You can get a ketone metre and test strips from most pharmacies. You would normally want to see >0.5 mmol/l as evidence of nutritional ketosis.  This is my preferred method of monitoring, if you feel inclined.
• Breath ketones – this technology has recently become available.  I don’t have one yet but as far as I can tell it measures breath acetate. I’ll try and suss this one out in due course.

Final words

Getting fat adapted is a great self experiment, at least to understand that you don’t have to run the brain on 100% carbs. There is another way, and it is what has defined you as a human for many many generations, so you may as well have that system operational.

I’m not saying you have to be, or it is even good to be, in a constant state of nutritional ketosis. Just that you can and should try and develop the metabolic flexibility to easily move in and out of that state. We don’t have all the answers about how that flexibility changes and the best ways to adapt.  That’s why we do research into this.

But try it and see how you go. Eat more fat and more salt, monitor carbs and protein carefully, and set aside some time to feel a bit low, and you will come out with a whole new appreciation for how your brain and body function optimally.