What is a Low Carbohydrate High Fat Diet? And why EVERYONE should know about it!

How can this be healthy? 

The dogma of the last 50 years has been that fats are "bad" and should be largely avoided. The research of the last 15-20 years is now gaining traction in mainstream and showing fat is NOT the demon it has been portrayed. The most recent evidence of this is the recommendation of the US Department of Agriculture's own Advisory Board to scrap the current cholesterol guidelines because dietary intake of cholesterol is not valid or supported by the science. So if we accept the cholesterol warnings are wrong, what about fat and saturated fat?

What is a Low Carbohydrate (Low Carb) High Fat Diet?

Years ago as a graduate student I heard about a research study on the Atkins Diet that was being conducted in the human performance lab where I worked. I was intrigued with what I heard. A low carbohydrate diet higher in protein and fat intake, especially saturated fat, that results in an increase in lean muscle mass, decreased fat mass, and improved blood lipid profile. Crazy! So I had to try it for myself. J

That was more than 15 years ago and the research on low carbohydrate diets has grown and been adopted not just by clinical populations, such as diabetics to improve their health, but also a growing number of professional and recreational endurance athletes to improve performance.

So what is a Low Carbohydrate diet? And more specifically, what is a Low Carbohydrate High Fat (LCHF) diet?

What is a Low Carbohydrate versus a Low Carbohydrate High Fat (LCHF) diet?

The current guidelines from the U.S. Department of Agriculture (USDA), recommends adult Americans consume 45 to 65 percent of their total daily calorie intake as carbohydrates. For someone consuming 2,000 calories a day, that would be 900-1,300 calories of carbohydrates.   This equals 225-325 grams of carbohydrates. (http://www.cnpp.usda.gov/dietary-guidelines-2010)

So like limbo, how low do we need to go, to be on an effective Low Carb diet?

Compared to the USDA’s recommendations, pretty low. For example, the Atkins Diet (a low carbohydrate diet) has an initial “Induction” stage of 2 weeks during which carbohydrates are restricted to 15-20g per day, in order to induce nutritional ketosis. (Note however, the Atkins Diet describes a process of gradually increasing carbohydrate intake over the ensuing months. In the second stage, called “ongoing weight loss”, you may increase your daily carbohydrate intake by 5g increments each week, as long as you are still experiencing weight loss. Over time you move into the 'pre-maintenance' phase, where you are still gradually increasing your carbohydrates intake from nutrient dense (not calorie dense) vegetables with some nuts and berries, up to the point at which you stop losing weight. From this process you will know how much carbohydrates your body will tolerate. Finally, when you have reached your weight loss goal AND have found the highest amount of carbohydrates your body will tolerate, you start the maintenance phase.

For LCHF diets, if we look at Jeff Volek (PhD, RD) and Stephen Phinney’s (MD, PhD) research (arguably the premier researchers on LCHF diets), below 50g per day is recommended. However, they caution in their book The Art and Science of Low Carbohydrate Performance, as do other authors, there can be significant differences between individuals. Some people may need to be below 20g (I’m one of these people), whereas others may do fine up to 100g per day. How much carbohydrates you should consume per day depending on a number of factors. Let’s look at each one.

1. Individual sensitivity, or tolerance, to carbohydrates. Personally, over the years I have found I am extremely sensitive to carbohydrates. While this means I have to keep my carbohydrate intake below 20g to stay in ketosis, it also means my strategic use of carbohydrates during training and racing feels like a massive energy boost!! So some people may be very sensitive to carbohydrates while others may be more insensitive. To find out where you stand you need to monitor your carbohydrate and protein intake and measure your blood ketones and your weight. If you’re taking in 50g of carbohydrates and your weight isn’t going down and you’re not in ketosis, you need to go lower.

2. What phase of the diet or training you are in. Some people may find that when their training load (a measure of the combined volume, intensity and frequency of their training) is higher, they can take in more carbohydrates immediately before and during exercise, and stay in nutritional ketosis. I have had excellent experiences with the superstarch UCAN in this manner. UCAN is a slow digesting carbohydrate that has a much lower impact on both blood glucose and insulin levels than other forms of carbohydrates. But in my experimenting I have found that taking in carbohydrates such as UCAN immediately before exercise has to be within 20 minutes of exercise AND I have to train for at least 2 hours, or I come out of ketosis. So to avoid this problem, I only take in carbohydrates if the session will be greater than 2 hours and after I’ve been running or riding for 30 minutes.

[Be aware that in the hour or so after exercise skeletal muscle is more sensitive to insulin , so taking in carbohydrates in the hour or 2 after exercise can cause a rapid uptake of glucose into muscle and that is detrimental to staying in ketosis and optimizing fat metabolism. This will be addressed in greater detail in an upcoming post. Stay tuned!)

In terms of diet phases, LCHF diets start with carbohydrate intake being reduced to below 50g per day, which induces nutritional ketosis after 3-5 days. But the goal is to actually move past this into a fat adaptation phase. So what is fat adaptation? How is fat adaptation different to nutritional ketosis?

When you are in Nutritional Ketosis (explained in greater detail below) your liver is producing more ketones than normal, but your brain AND skeletal muscle aren’t used to using these ketones for fuel. So your skeletal muscle is not directly using higher amounts of fat for energy. In order for this to happen, and to be in an optimal fat adaptated state (referred to as keto-adapted or fat-adapted depending on the author), requires 2-4 weeks of remaining in sustained nutritional ketosis. At this point, various physiological adaptations have occurred in the metabolic machinery of your muscles and brain to allow skeletal muscle to directly use fatty acids from the blood, and internal muscle stores, for fuel, sparing ketones for the brain. This is also the point where energy levels go up dramatically and you experience greater mental focus and clarity. You can see this reflected in your blood ketone measurements. If skeletal muscle is no longer taking ketones from the blood, ketone levels in the blood rise, allowing the brain greater fuel availability. In practical terms, at the start of a LCHF diet, your blood ketone levels will increase up to 0.5 to 1.0mM, but once you reach fat adaptation they will increase further to 1 to 3mM. Now you know you’re in an optimal fat burning state!

3. Type of Carbohydrates being consumed. It is VERY IMPORTANT to note that the TYPE of carbohydrates you consume are critical, not just how many carbs. For example, eating a couple of slices of white bread or a can of soda may be less than 50g of carbs, but the high insulin response to all the sugar can undo all the good work you have done keeping your total carb intake low. Insulin is a hormone released by the pancreas in response to rapid rise in blood glucose. I will explore and describe more on the roles of different types of carbohydrates and insulin on poor health and disease in a separate post. Stay tuned!

What is Nutritional Ketosis? What are ketones? How are Ketones made? Where do ketones come from?

You know you are consuming an appropriately low amount of carbohydrates if you are in nutritional ketosis. Nutritional ketosis refers to sustained, higher than normal level of ketones (or ketone bodies) in your blood. If you were to measure your blood ketone levels with a portable ketone meter such as the one shown here, you would get values between 0.5 to 3.0mM. When your blood sugar (glucose) drops to a point where there isn't sufficient amounts of sugar to meet the bodies needs for energy, more fat is released from your fat cells into the blood (as fatty acids) so they can be used for fuel. These fatty acids travel through the blood to your liver where they are broken down and converted to ketones (aka ketone bodies). Ketones may also, to a much lesser extent, be produced by the liver in response to the breakdown of certain amino acids from protein. Excess ketones are excreted from the body in urine.

So these levels of ketones in your blood means you have chronically low levels of glucose in your blood AND stored as glycogen in your body.

However, if you have heard of the condition - ketoacidosis or diabetic ketoacidosis – this is not the same as nutritional ketosis, and refers to a pathological condition in which the liver is producing ketones at a severely high rate in response to some disease state, such as diabetes, severe and prolonged alcoholism, or starvation. Blood ketones for these individuals are in the range of 15-25mM. As you can see, these levels are 5 or more times higher than someone in nutritional ketosis. At such high levels, ketoacidosis can result in a series of negative health effects due to the prolonged and severely elevated levels of ketones. Someone in nutritional ketosis at much much lower levels of ketones does not have these issues or concerns. But rather, nutritional ketosis refers to the process of your body switching to the production of ketones at a level it can use for fuel, and also switching to using predominantly fat for fuel. IN this state, excess ketones are excreted from the body.

As I said earlier, one of the great things about nutritional ketosis is that it is something you can measure with a ketone meter using a very small drop of blood. You can also use ketone strips designed to test urine levels of ketones but these are far less accurate, although they are much less expensive than blood (10 cents vs $2 per strip). So you have a hard and fast number you can look at that says you are, or are not, in ketosis and as such, you are, or are not, consuming a sufficiently low amount of carbohydrates.

(NOTE: The kicker here is that if you consume too much protein, the liver will convert it into glucose and you will not be in nutritional ketosis. So keep protein intake to a moderate amount – 0.6 to 1.0g per pound of lean body mass.

Why would someone choose to be on a Low Carbohydrate of Low Carb High Fat (LCHF) Diet?

In short, excess consumption of carbohydrates can lead to a host of health problems including obesity, metabolic syndrome, heart disease, and diabetes. For athletes, carbohydrate consumption can lead to GI distress and limit endurance performance by reliance on our very limited carbohydrate stores and inability to consume enough carb calories as we need to fuel our performance.

So while some people may choose to follow a LCHF diet to lose weight others may wish to improve their health by reducing risk factors associated with diabetes, high blood pressure, and metabolic syndrome. Endurance athletes on the other hand may be looking to optimize their fat burning potential to increase endurance and performances. And still further, others may be looking to improve their cognitive function through a steady supply of ketones for improved brain functioning.

Other benefits that have been reported include increased energy levels, faster recovery times from training, reduced illness and reduced severity of illnesses, and better mental clarity. I have personally experienced all these and became most aware as I realized my training consistency had gone up as I was sick far less than I used to be. Having 4 children, coughs, colds and sneezes happen at our house, so I would take time off more often than I would like with upper respiratory tract infections and sinus infections. Since starting LCHF living I can’t remember the last time I took time off because of an illness. Being a lazy bastard is another issue I have to deal with.  J

What foods should I avoid on a Low Carbohydrate High Fat (LCHF) Diet and which ones can I eat?

A Low Carb High Fat diet is not about just eating bacon and eggs. My diet contains a large amount of green leafy vegetables and a much lower bacon intake than I initially consumed. Generally, you should avoid the following (stay tuned for an updated and complete list coming soon):

• All refined carbohydrates and processed foods including, but not limited to bread, pasta, cookies, cake, candy, etc
• sugar-sweetened sodas and drinks,
• all fruit juice and fruit drinks,
• grains in any form,
• fruits (although a small amount – ¼ cup of berries per day is well tolerated)
• high carb and starchy vegetables eg potatoes, sweet potatoes, etc
• milk
• legumes (beans, lentils, peas)

Foods you can enjoy (but like any diet, do not over indulge):

• Dark green leafy vegetables,
• Butter and cream,
• Bacon,
• Eggs,
• High fat cuts of meat,
• Avocado

Foods you can enjoy in limited amounts:

• Nuts and some seeds (lots of micronutrients but some carbs so limited to ¼ cup per day)
• Berries (incredibly nutrient dense but some carbs so limited to ¼ cup per day)
• Hard Cheeses (1 – 2 oz per day)

Some low carb diets such as Atkins focus on a higher protein intake rather than fat and on these diets there is a greater intake of protein in the form of meats, poultry, fish and eggs.


A key element to living a LCHF lifestyle is to not over indulge and to eat only when you are actually hungry. I will often eat only 2 meals a day or go 16-18 hours without eating. I don’t do this intentionally. I have just found that on days when I don’t exercise much, I’m not hungry. So each time before you eat, simply ask yourself, “Am I actually hungry, or am I in the habit of eating at this time?” Sometimes, we want to eat because we have been indoctrinated into the idea we are supposed to eat small but frequent meals. Living a LCHF lifestyle you will find this is not the case. 

Things To Remember When Starting or Living Low Carbohydrate High Fat (LCHF)

1. This is not an, “All You Can Eat Fat Diet” nor is it an “All You Can Eat Protein Diet”. The key to success, whether your goal is performance, health or weight loss, is consuming a LOT of low carb vegetables while staying under 50g of carbohydrates per day and moderate protein (0.6 to 1.0g per pound lean body mass). Monitor what you consume, blood ketones and your body weight to know if you are on track.
2. Fatigue is inevitable in the first stage of ketosis. Go into it knowing you will likely have 1-3 weeks of feeling fatigued. You will need to dial back your training, maybe a lot, in this phase. So don’t try this in any other part of your season except the off-season. But know this is temporary and you likely will push through this phase faster as your demand for fuel is higher, forcing the body to adapt more quickly. The fatigue you feel is due to a combination of factors including:
   1. Sodium loss with ketones. So add more sodium to your diet. An additional 1-3g may be necessary. (As always, start at the bottom of this range and increase as necessary.)
   2. A few words on headaches. When I was doing the Atkins Diet study in grad school, I experienced a great deal of fatigue and also headaches. At that time it wasn’t widely known that you could lose high amounts of sodium as the body excreted the excess ketones from your body. So if you do experience headaches, simply add some salt to each meal and try consuming chicken or beef broth made from scratch or bouillon. Another reason for your headaches might be that you are consuming too many carbohydrates to be in ketosis and not enough carbohydrates to supply the brain with enough fuel. So if you have headaches and are not in ketosis, you’re probably not getting enough sodium and too many carbohydrates.
3. Too much protein. Remember, your body can convert protein to glucose, so to keep your bodies glucose levels low do not fill up on protein. Too much protein also means you likely won’t eat enough fat. Fat should be 65-75% of your calories.
4. Muscle cramps mean add Magnesium. Athletes may not be taking in enough magnesium in their diet because they grill their meats (a good amount of magnesium is lost in the drippings that end up being thrown away) and those on a LCHF diet may suffer more from this. To avoid this, use the drippings in your pan to make gravy and increase your intake of green leafy vegetables. But if you still get muscle cramps or prolonged fatigue look at adding a magnesium chloride supplement to your diet. Volek and Phinney suggest 3 tablets per day for 20 days of Mag-64 or another generic of Slow Mag.
5. Be diligent in tracking your carbohydrate intake. There are a number of free and good phone apps and online software you can use. It might be a pain to do this for a few weeks until you recognize where your carbohydrates are coming from, but it is definitely worth it!
   1. And remember, you may need to go lower than 50g per day, or be one of the lucky ones that can tolerate up to 100g and still be in ketosis.

I hope you find this blog post helpful. Please let me know what you think in the comments below and if you have any questions.


And if you are interested in how the Atkins Diet went for me in grad school, good and “bad”. I did increase my lean muscle mass, decreased my fat mass, my blood lipids improved even though they started off in great shape, but my running suffered significantly. I suffered a lot of fatigue. But knowing what we know now about the need for higher sodium intake and magnesium I think it would have been a different story. Right now on a LCHF diet I feel great and training and racing are going well!


Lastly, as always, consult with your medical practitioner before adopting a Low Carbohydrate High Fat lifestyle to ensure it is safe for you and you do not have any cholesterol or other pathologies that would preclude you from enjoying the many benefits of LCHF living.