A few months back, the following tweet from triathlon legend Dave Scott caught my eye:

It always amazes me how folks fear a new paradigm for sports nutrition. Unless you own a sugar-based nutrition company, why WOULDN’T you experiment w/ #LCHF It works when implemented properly … even at high intensities.

I’m not sure whether Dave meant this question rhetorically (after all, there’s no question mark), but I took it literally and personally. As a competitive endurance athlete who takes seriously the role of diet in endurance performance, I had to ask: why haven’t experimented with a low-carbohydrate, high-fat diet?

The answer, I decided, could be distilled to a single word: risk. I believe that switching from my current way of eating to LCHF would carry an unacceptably high risk of causing problems. For me, a better question than the one Dave asked is, why would I experiment with LCHF? My current diet does not limit my athletics in any way that I can identify. When I train harder I get fitter and when I rest I recover. I feel good physically pretty much all day every day. At age 47 I am as lean as I was when I was 27. If it ain’t broke, as they say. . .

Meanwhile, on the other side of the equation are a host of negatives outcomes, some guaranteed, others likely, that are associated with jumping onto the LCHF bandwagon. Nearly all athletes who do so feel like crap initially and experience a significant decline in training capacity and performance. Some come out the other side eventually, others don’t. The diet is extremely restrictive and monotonous and socially isolating. (“Hey, Brad! Do you want to come out to dinner with us? We’re going to that Italian place.” “Uh, well, you see. . .”) And the physiology is inescapable: Eating LCHF will make your muscles better at burning fat and much worse at burning carbohydrate, hence more dependent on fat, which requires greater amounts of oxygen to metabolize, thereby increasing the energy cost of moving at any given speed.

Those are the guaranteed outcomes. The potential outcomes that seem to affect some but not all LCHF eaters include unfavorable changes in blood lipids, mood disturbances, vertigo, skin problems, caffeine intolerance, and panic attacks. The long-term health effects of eating in this extremely unbalanced way are largely unknown, but a recent, large epidemiological study found that, on average, men and women who get less than 40 percent of their daily calories from carbs die four years younger than do those who get between 40 and 70 percent of their calories from carbs.

Elite endurance athletes don’t shy away from this diet because they are afraid of news things. To the contrary, no group is more eager to gain a competitive advantage through early adoption of new methods. Instead, the vast majority of pros choose to keep their diet carb-centered because, with their livelihood depending on their performance, they can’t afford to try “new” things with such an obviously poor risk-reward ratio as LCHF.

A recent case study indicates they are wise to do so. For a period of 32 weeks, a professional triathlete who switched from his normal, lacto-ovo vegetarian diet to LCHF was monitored by Spanish exercise physiologist Iñigo Mujika. Within the final third of this period, the athlete raced three times, finishing 18thin a half-Ironman with his worst time ever for that distance, then finishing 14thin a full Ironman with his second-worst time ever for thatdistance, and then DNF’ing his next race. Having had enough of LCHF by this point, the athlete went back to his normal diet. Just five weeks later he took second place in an Ironman.

This case study challenges several tenets of the LCHF doctrine. One of these is the notion that only athletes who, as Dave Scott suggested, fail to implement the diet properly fail to benefit from it. But Mujika’s subject was an experienced and knowledgeable professional athlete with all the attending resources and scientific support. Mujika reported 95 percent compliance with the diet’s strictures across the 32-week period. LCHF advocates also like to explain away the disasters that so commonly befall athletes who try it by claiming they didn’t give it enough time. I’m sorry—if 32 weeks isn’t long enough, then forever isn’t long enough.

The primary reason this particular athlete switched to LCHF was that he suffered from debilitating GI issues during races, and it is another popular tenet of the diet’s doctrine that it cures these issues. The subject of the case study experienced no improvement in GI symptoms during races on LCHF. This shouldn’t surprise anyone, as the two main causes of GI distress during long endurance events are the stress of the events themselves and a genetically-rooted susceptibility, neither of which can be changed by any diet.

Here is where LCHF advocates predictably say, “But this is just a case study. We’re talking about one athlete!” The problem with this objection is that each of us is one athlete with only one body to care for and limited opportunities to compete each year. If LCHF works best for 90 percent of athletes, it is remarkably unlucky that the athlete chosen for this case study was among the few for whom it doesn’t work. Is this the assumption you want to make as an athlete who cares most about your fitness and performance? I think it’s far more reasonable to see this case study as yet more firm evidence that LCHF is risky.

This was not intended to be another one of my rants against LCHF for endurance athletes. The point I want to make in referencing it is that, although this way of eating does appear to work okay for some athletes, it is high0risk. So are a lot of other diets and nutritional measures that endurance athletes try in pursuit of better performance. Reflecting on Dave Scott’s tweet caused me to realize that the approach to endurance nutrition that I advocate is really a risk-minimization approach.

If you adopt and follow the five habits of the Endurance Diet, you will not and, indeed, cannotgo off the rails in the way that so many LCHF athletes, plant-based athletes, and other athletes who choose unbalanced diets of one kind or another do. To refresh you memory, these habits are:

EAT EVERYTHING

Consistently including all of the major food types in your diet minimizes your risk of being taken down by one of the nutritional holes that open up when things like meat/fish and grains are eliminated.

EAT QUALITY

This habit is about centering the diet on unprocessed, natural food types (e.g., nonfried vegetables) and limiting intake of processed foods (e.g., refined grains). Many LCHF eaters pay no attention to quality, loading up on processed animal products such as cured meats and mayonnaise that have proven negative health consequences.

EAT CARB-CENTERED

It’s just a fact: The safest place to start with your macronutrient balance, if you’re an endurance athlete, is carb-centered, which simply means including high-quality carbohydrate-rich foods in most meals and snacks. Lots of LCHF eaters claim they switched to this way of eating because a carbohydrate-centered diet didn’t work for them. This claim never stands up to scrutiny. It was sweetsand refined grainsthat didn’t work for them, not carbs in general. I’ve never dealt with an athlete who couldn’t make a carb-centered diet work for him or her by combining it with Habit #5 (below).

EAT ENOUGH

This habit is about relying on the body’s built-in appetite signals to regulate the amount of food you eat instead of counting calories. In my experience, calorie-counters are at much greater risk of eating too little, which is far more detrimental to endurance performance than eating too much.

EAT INDIVIDUALLY

Most extreme diets are one-size-fits-all. The Endurance Diet is not, and this is another way in which it manages risk. Do grains generally not agree with you? Fine. Then practice Habit #3 (“eat carb-centered”) by getting most of your carbs from fruit and starchy vegetables. Forcing yourself to eat exactly like every other follower of whichever named diet you choose to follow brings with it great risk of forcing yourself to do something that doesn’t work for you individually.

Woven into these five habits are two further principles that also serve to minimize risk in eating for endurance. Framed as edicts, they are (1) Keep things as simple as possible and (2) don’t change anything in your diet that you don’t both wantand needto change. The more unnecessarily complex you make your eating habits (e.g., intermittent fasting) and the more things you change (e.g., completely tossing out your current habits and going all-in with LCHF or some other unbalanced one-size-fits-all) diet, the likelier it is that you will create a health- or fitness-harming new problem that did not exist previously.

A certain amount of risk is inherent in endurance athletics. You have to train hard to attain peak fitness, and hard training brings with it the risk of injury and the risk of illness. Don’t let your diet compound these risks unnecessarily.