By Dr. Mercola
Endurance athletes have been told for decades that carb loading is necessary to perform at the top. To suggest otherwise has long been regarded as heresy — or at the very least as foolish.
But quietly, many athletes got wind of a new type of diet — a high-fat, low-net carb (total carbs minus fiber) diet — that was fueling the fittest among them. Many top athletes quickly became converts, trading bowls of pasta and oatmeal for eggs and avocados.
As their performance improved, along with their health, most athletes kept quiet, following their seemingly sacrilegious diet in the closet.
Some didn’t tell because they wanted to avoid potential backlash, but many others wanted to keep their newfound diet a secret — why tip off competitors that eating a high-fat, low-net carb diet was giving them a major competitive edge?
In the documentary film “Cereal Killers 2”, above, you can watch world-class triathlete Sami Inkinen’s story firsthand. Once teetering on the edge of diabetes, Inkinen learned that by changing his diet he could switch from burning sugar to burning fat as fuel, and therein lay the key to reaching new performance heights.
What’s Wrong With Carb Loading?
The idea behind carb loading is to saturate yourself with carbs so your muscles will have plenty of glycogen to use as fuel while you exercise. Carbs are stored in your muscles and liver in the form of glycogen, which your body uses as fuel. Once this fuel runs out, fatigue sets in and your performance suffers.
Carb loading helps to increase your glycogen stores so that you’ll have more energy and be able to run farther before running out of fuel. However, if you’re burning carbs as your primary source of fuel, you’ll still need to refuel during a marathon.
This is why you’ll hear Inkinen’s wife Meredith explain how she was convinced to eat oatmeal prior to cycling events and then to consume carb-rich energy gels during the race to prevent bonking (a slang term for “hitting the wall” or running out of energy during endurance events).
Bonking is a common problem when you rely on sugars for fuel. The fact that you still may need to refuel your body in the midst of the event, even after carb loading prior to it, makes the notion of carb loading rather redundant and unnecessary, but that’s beside the point.
As Meredith noted, she hated the way the gels made her feel, and there’s a fundamental reason for this. Carb loading may temporarily increase exercise performance, but these benefits may be canceled out by water weight gain (your body stores water with carbs) and bothersome digestive symptoms.
Not to mention, there’s a far better fuel for your body — during endurance events and even casual exercise — fat.
Why Your Body Thrives When Using Fat as Fuel
Only when your glycogen stores are depleted, will your body move to using fat as its fuel. And it’s this fat-adapted state that results in improved energy utilization and other benefits, such as stem cell regeneration and tissue repair, along with decreased body fat, reduce inflammation, and increased insulin sensitivity.
If you carb load prior to exercise, you will actually be inhibiting fat burning and many of the metabolic benefits of exercise, even if it enhances your performance temporarily.
It doesn’t matter if you’re an athlete or not — your body will thrive when using fat as fuel. This was demonstrated in the first “Cereal Killers” film, which was released in 2014.
In the first film, Donal O’Neill switched over to a diet where 70 percent of his calories came from healthy fat — most of it in the form of macadamia nuts (my personal favorite) — and the remaining 30 percent from protein and fibrous fruits and vegetables. Over the course of 28 days, O’Neill:
Lost weight and body fat
Felt more energetic and improved his athletic performance
Improved his blood pressure, cholesterol, and other measurements to the point that he no longer had any non-genetic risk factors for heart disease
Increased his lean muscle mass
Increased his resting metabolic rate
Anti-Inflammatory Benefits and More
O’Neill’s total cholesterol and LDL (low-density lipoprotein) levels while on the diet were also noteworthy. They went up — however, once they tested the LDL particle numbers, the results showed that his LDL particles were the largest type known, and he had virtually no small LDL particles at all. Large LDL particles are not harmful.
Only small dense LDL particles can potentially be a problem, as they can squeeze through the lining of your arteries. If they oxidize, they can cause damage and inflammation.
Further, O’Neil’s markers for inflammation were virtually nonexistent, showing that he had virtually no inflammation in his body at all.
He also broke his own athletic record during the experiment and referred to his renewed sense of vigor as feeling like a “spring lamb.” It clearly showed the benefits of a high-fat, low-net carb diet for athletes, many of whom are still convinced that this type of diet will make them heavy and sluggish.
On the contrary, this high and sustained energy is a hallmark of ketogenesis, where your body is burning fat rather than sugar as its primary fuel. When your body burns fat, you don’t experience the energy crashes associated with carbs.
Eating a High-Fat Diet Helps You Burn Fat
A ketogenic diet is one that shifts your body’s metabolic engine from primarily burning carbohydrates to burning fats as its primary fuel. Your cells have the metabolic flexibility to adapt from using glucose for fuel to using ketone bodies, which come from the breakdown of fats — hence the name “ketogenic.”
Another term for this is nutritional ketosis. As an aside, many types of cancer cells do not have this adaptability and require glucose to thrive, which makes the ketogenic diet an effective therapy for combating cancer.
A high-fat-burning diet requires that 50 percent to 70 percent of your food intake come from beneficial fats, such as coconut oil, MCT oil, grass-pastured butter, organic pastured eggs, avocado, tallow, lard and raw nuts (raw pecans and macadamia nuts are particularly beneficial).
One of the fastest ways to prevent nutritional ketosis is by consuming sugar or net carbs, which is total carbs minus fiber. If you’re like most Westerners, whose diets are typically heavy in sugars and other carbs, then you’ve lost your ability to burn ketones efficiently.
With an ever-present supply of carbs, your liver downregulates the entire fat-burning process because it hasn’t needed to. Your fat-burning engine has been suppressed. If you eat the standard American diet, chances are you’ve lost your ability to burn body fat, despite carrying around a probably more than adequate supply of it.
By the way, it’s not only endurance athletes that experience bonking; you may experience it too and probably have if you’ve ever felt like your energy was just wiped out and you were dead on your feet. So, while it may sound ironic, eating more fat and fewer net carbs will ultimately help your body to burn more fat. There are other methods that can help you switch over to fat-burning mode too.
Intermittent Fasting Can Help You Switch Over to Burning Fat for Fuel
Supplying your body with carbohydrates day in and day out is like carb loading in a sense. You’re constantly supplying your body with carbs, which are converted into glycogen. Since you virtually never run out of glycogen stores, your liver has no need to start tapping into your fat cells — and so it doesn’t.
One reason so many struggle with their weight (aside from eating processed foods in lieu of real foods) is because they rarely if ever skip a meal. As a result, their bodies have adapted to burning sugar as the primary fuel, which down-regulates enzymes that utilize and burn stored fat.
Intermittent fasting can change that. By abstaining from food, your liver runs out of glycogen and then, just like that, starts to use up glycogen stored in your fat cells. Now, you needn’t fast for long periods of time. In fact, I wouldn’t recommend long-term fasting at all.
As a general rule, I recommend a new type of intermittent fasting that I call Peak Fasting, which, unlike other versions of intermittent fasting, is done every day (you can certainly cycle in off days due to your schedule or social commitments, however).
The process is simple. Stop eating three hours before bed and don’t have your first meal until 13 to 18 hours later. Measure your blood sugar at that time. You can do this every half hour, and when it starts to dramatically rise, this is an indication that you need to break your fast and eat food, as you are starting to break down your lean muscle mass to raise your blood sugar.
How Long Should You Use Peak Fasting?
If you’re overweight and/or have symptoms of insulin and leptin resistance, such as high blood pressure, high cholesterol or type 2 diabetes, continue intermittent fasting until your insulin/leptin resistance improves and your weight, blood pressure, cholesterol ratios, or diabetes normalizes.
As an example, if you need to lose 50 pounds, you’re looking at about six months or so of intermittent fasting, after which you can revert to eating more regularly. After that, all you need is a “maintenance program.” Keep track of your markers, and if they start sliding, go back on the fasting program of your choice again for a number of weeks or months.
Alternatively, you could intermittently fast for say one month, twice a year, as a form of maintenance. Another strategy you can try is exercising while in a fasted state, which, when using Peak Fasting, would mean exercising first thing in the morning. One study found, for example, that fasting before aerobic training leads to reductions in both body weight and body fat, while eating before a workout decreases only body weight.1
But once you reach your ideal body weight it appears likely that there is long-term benefit to continue Peak Fasting indefinitely along with a low-net-carb, moderate-protein, and high-quality fat diet. There is compelling research to suggest this may be one of the most powerful ways to slow down the aging process and prevent most chronic degenerative diseases.
Athletes Ditching Carb Loading
Athletic superstars like NBA players LeBron James and Ray Allen claim to have switched to a low-carb diet with beneficial results.2Other athletes jumping onto the high-fat, low-carb diet include Ironman triathlete Nell Stephenson, pro cyclist Dave Zabriskie, and ultra-marathoner Timothy Olson.
Former Ironman triathlete Ben Greenfield is said to have followed a ketogenic diet while training for the 2013 Ironman World Championships and experienced improved stamina, stable blood sugar, better sleep and less brain fog.3 Again, this might sound surprising to carb-loading enthusiasts (or be brushed off by carb-heavy sports drink makers like Pepsico who makes Gatorade) but it makes perfect sense metabolically speaking.
When You Burn Fats, You Don’t Run Out of Fuel
“Cereal Killers 2” touches on research by Jeff Volek, Ph.D., a registered dietitian and professor in the Human Science Department at Ohio State University, and Dr. Stephen Phinney, a physician and true pioneer in this field, who has studied low-carb diets even longer than Volek.
Both have done enormous work in the field of high-fat, low-carbohydrate diets, investigating how they affect human health and athletic performance. They’ve also co-authored the following books, which I highly recommend if you’re interested in reading more about this topic: “The Art and Science of Low Carbohydrate Living” and “The Art and Science of Low Carbohydrate Performance.” As Volek stated:
“To be quite frank, they’re [endurance athletes] challenged from a fueling perspective because if they’re eating carbs, they’re inhibiting their ability to burn fat optimally. They’re putting themselves in a situation where they’re increasingly dependent on providing more carbs.
You can only store a limited amount of carbs in your body as glycogen, about 2,000 kilocalories, and if you’re exercising for more than a couple of hours, you’re burning through the majority of that stored carbohydrate.
That’s when an athlete hits the wall. We know that’s associated with obvious decrements in performance. How do you avoid that? You can carb-load. That’s been the traditional recommendation; to try to pack even more carbs into your muscles … but that will only delay exercise fatigue by a half hour or so. That doesn’t really solve the problem.
It actually exacerbates the problem in some ways. The alternative is to train your body to burn more fat. If you’re burning fat and sparing carbohydrates, you don’t hit the wall. That’s one of the most commonly perceived benefits of a low-carb diet for athletes.”
Athletes who adopt this strategy can become exceptionally good at burning fat. Even if they’re not eating calories during exercise, lean athletes have at least 20,000 to 30,000 kilocalories on their body in the form of fat tissue that they can access during exercise. That’s more than enough to finish even a 100-mile race. So from a fueling perspective, it makes sense that you’d want to burn fat as opposed to carbohydrate.
Low-Net-Carb Diet Beneficial for Athletes and Non-Athletes
Mounting evidence suggests high-fat, low-net carb diets may be the key that many people have been looking for, as it solves more than one problem. Not only does it help you shed excess body fat, it does so while simultaneously improving metabolism, boosting overall energy levels, lowering inflammation, promoting optimal health and maximizing longevity in a number of different ways.
If you’re interested in optimizing your fat-burning system, one effective way is to limit your net carbs (total carbs minus fiber) to under 30 to 40 grams per day and do not consume more than 1 gram of protein per kilogram of lean body mass. At the same time, you’ll want to increase your intake of healthy fats.
Many will benefit from consuming 50 percent to 85 percent of their daily calories in the form of healthy fat from avocados, organic grass-fed butter, pastured egg yolks, coconut oil, and raw nuts such as macadamia, pecans, and pine nuts. You can also consume as many low net carb vegetables (ideally organic) as you like. What you’ll notice is that consuming a diet like this means eating real foods and letting processed foods fall by the wayside.
As mentioned, you can kick the entire process up a notch by also using Peak Fasting, at least for a finite period of time while your body returns to a balanced state. After that, assuming you’re still eating right, you’ll only need to intermittent fast on a maintenance basis. If you’re an athlete, or even if you’re not, I’d love to hear your stories about how your health changed when you switched to fat-burning. Please do share in the comments section below.
Founded Mercola.com in 1997 which is now the most visited natural health site on the web with 1.5 million subscribers. My site is grounded on providing the latest health information and providing practical health solutions.