Dear Mark: Carb Refeeds, Electrolytes, Vegan Orthodox Fast, Grinding vs Playing, and Fast Twitch Fibers

Back on the old blog, I used to answer questions from readers every week. We called it “Dear Mark,” and people still ask me about it. So I decided to bring Dear Mark back.

A few weeks ago I asked for questions over on X. Today, I’m answering some. Going forward, I’ll open up comment sections for paid subscribers to ask questions and I’ll answer what I can. Some will be quick replies, others will be longer write ups like today’s post. We may do some other cool stuff like in person meetups or live AMAs. We’ll see. Still feeling things out.

Let’s go:

Many years ago, I wrote about carb cycling or periodic carb refeeds when on a low-carb or ketogenic diet. Short story: they aren’t always necessary but yes, they can help. How do you know if you’ll benefit from them? Let’s go down prime candidates for who might benefit from a carb refeed/cycle:

People who have stubborn fat to lose and have hit a plateau for a long time. This situation involves people who are pretty close to their goal weight and have used a lower-carb diet to get there, but they just haven’t lost any weight for a while. Maybe even weight is going up a bit. For them, the cause is probably low levels of a hormone called leptin. Leptin is a hormone of abundance. It increases energy expenditure and has a cascade of beneficial effects on your metabolism. The presence of body fat causes leptin secretion, as does food intake (both signaling abundance). So if your body weight is “low” and your food intake is restricted, leptin can drop and stall weight loss.

A big carb refeed with lower fat levels is one of the easiest ways to boost leptin. It could be a single meal. You could just eat high-carb, low-fat on training days or after workouts. Or you can just do it over the weekend and eat lower carb the rest of the week. These are all effective ways to insert carb refeeds.

Why low-fat?

Dietary fat has no effect on leptin levels. Carbohydrate is the macronutrient that increases leptin secretion the most. Think white rice and plain potatoes rather than fried rice and mashed potatoes with a stick of butter. Extra fat gets in the way, contributing energy without increasing leptin secretion.

Why on training days?

Exercise increases leptin transport, making any leptin you do make more effective and efficient. Training will also deplete glycogen stores and increase insulin sensitivity, allowing most of the carbohydrates you eat to go into muscles for later use rather than inhibit fat loss.

High-output athletes who have been low-carb for a long time can also benefit. There’s a classic story from the early days of CrossFit. CrossFitters who were eating low carb strict Paleo and hitting the WODs hard every day but had trouble sleeping, were still a little pudgy, and weren’t making any PRs. They started eating ice cream at night after workouts, and they would wake up leaner and perform better the next day. They were probably just too low-calorie overall, trying to eat too clean while supporting massive output. The rest of the diet was normal. All they did was add a bowl of ice cream at night, and the combination of carbs, calories, fat, and low-stress pleasure probably gave their body the spark and energy needed to perform.

I’m known as a low carb guy who thinks you should earn your carbs, and that remains true. But I’ve also said that you should eat the carbs you earn. If you are expending tons of energy doing high intensity training at a high volume, you’ve “earned” the cabs and should eat them. There’s no reason to abstain from them if they’re just going to go into your glycogen stores (which you’ve just emptied).

Don’t overthink it too much. My philosophy on electrolytes is very simple: replace what you sweat out.

I didn’t pay that much attention to electrolytes when I lived in Malibu because it was a dry, mild climate. Sweating was something you decided to do. It wasn’t compulsory. You were in the sauna or you were working out, and that’s when you’d sweat. But if you were just hanging out, walking around, not doing anything particularly intense, you weren’t going to sweat all that much.

In Miami, simply stepping outside makes you sweat. If you work out outside, like doing a stand-up paddle session or a fat tire bike ride, you're going to sweat more than you’ve ever sweat in your life. If you walk ten minutes to dinner, you’re going to sweat. Sweating is a way of life in Miami.

I was dragging my first couple weeks in Miami trying to maintain my normal activity levels. Noticed that food wasn’t tasting “salty” like it usually did because I was losing so much sodium through sweat. Bumped my salt intake back up and felt 20 years younger.

There are a few conditions that really increase electrolyte loss. Sweating is the obvious one, whether through ambient heat, humidity, sauna use, or exercise. Another is glycogen depletion. Every gram of glycogen comes with about 4 grams of water, so the more glycogen you lose, the more water and thus sodium, potassium, and magnesium you lose. You really have to replace those. A lot of the so-called "keto flu" comes from people just not getting enough salt after they’ve depleted their glycogen during the first week or two of ketosis (where you typically shed around 3 grams of sodium per day). That’s why LMNT was created by Robb Wolf, to address that issue.

Intense training, especially higher-volume lifting sessions, interval training, CrossFit WODs, and any other activity that combines moderately high intensity with high volume, will deplete glycogen, deplete water, and therefore deplete electrolytes. Combine those with heat, humidity, or post-workout sauna, and you compound the issue. This isn’t “bad,” it’s actually a good sign, but it does mean you have to replace what you’ve lost.

Anytime you feel “depleted,” it’s often a salt issue.

There are about a hundred different electrolyte powders on the market now. I like LMNT, personally. But before LMNT introduced a decent amount of sodium, you had to make your own. Everything else was way too under-dosed. My go-to electrolyte mix was:

Cup of coconut water

Juice from 1-2 limes or lemons

TB blackstrap molasses

Teaspoon of kosher salt

Water to taste

The coconut water gives you potassium. The lemon juice gives you flavor. The molasses gives you a little glucose plus a ton of magnesium, calcium, and potassium. The salt gives you sodium. And water gives you, well, water. This is an incredible “sports drink” if you don’t want to buy a product.

Right off the bat, going vegan for deep, spiritual motivations that speak closely to you, that stir something in your soul is going to be less deleterious to your health and metabolism than doing veganism for misguided reasons like “it’s healthier” or “it’ll save the planet.” Even though I’m not religious at all, and I am not vegan at all, I think that’s probably the most legitimate reason to go vegan: to fulfill your spiritual obligations.

But you do want to do it in a way that is least damaging.

I don’t know exactly how Orthodox Christianity works or how long your periods of fasting last, but if it’s anything more than a week, I would consider supplementation.

Creatine: 5-10 grams per day, only found in meat and fish. Vegetarians and vegans who take creatine enjoy better cognitive function, improved physical performance (more reps in the tank). Drink plenty of water, as creatine requires water for storage in the muscles.

Taurine: 1-2 grams per day. An amino acid that is very difficult to find in non-animal foods. Important for muscle function, brain health, mitochondrial energy production, stress resistance.

Carnosine: There’s a “chicken extract” supplement that’s popular in Asian countries as a mood enhancer. It’s actually a carnosine supplement (and it works). Carnosine is also potent brain antioxidant and increases muscle endurance. We can make some, but we’re also supposed to get a good amount from the meat we eat, which is why vegans have been shown to have lower levels.

Algal oil: Maybe not important for short term fasts, but for anything over a couple weeks algal oil is a great source of long chain omega-3s (algae are ultimately how the larger marine animals get DHA and EPA).

Potatoes: If you’re purely going for protein quality, you can’t do much better than potatoes. It just so happens that potato protein is incredibly high-quality, rivaling animal protein. I know several people who periodically do all-potato diets for five to seven days, and they often find that they lose weight—mostly body fat—and maintain strength and performance in the gym despite eating lower absolute levels of protein. Yes, potatoes are a good source of protein when you’re forced to eat a vegan diet.

What you do is you get a bunch of potatoes, you bake or boil them, and then you store them in the fridge. Then whenever you need a potato, it’s ready to go. Slice it up and quickly sauté, make potato salad, etc. They form resistant starch in the fridge, and then when you eat them, you have that prebiotic substrate that promotes butyrate production in the gut, increases satiety and insulin sensitivity, and can offset some of the glucose load that potatoes usually provide.

I won’t tell you to bother with a bunch of vegan protein powder blends. Sure, the right mix of pea, rice, and hemp protein will satisfy your amino acid requirements, but after the week-long fast you’re left with a bunch of powders taking up counter space. You’re better off using the week as a true fast from high protein intakes.

The way I see it, grinding is a young man’s game. Grinding is for when your hormonal milieu is optimal and your tissues are strong and supple and resilient enough to be broken down and then come back stronger.

The game of fitness is like climbing a mountain. The earlier you start and the harder you grind at the beginning, the taller the mountain you can summit. The higher you go, the higher your “peak” fitness, the easier the descent will be. You have more muscle, more cardiovascular fitness, more strength, more bone density that you accrued during your prime “grinding” years. And now? Now you can coast.

Once you’re on the downward slope, you want to take things easy. You don’t want to grind the descent. Push too hard and you might slip and start sliding down the scree faster than you want. You might even suffer something catastrophic. Instead, enjoy yourself. Maintain what you have.

So yeah, the grinding is important when you’re young and can handle the stress because it gets you to new heights. But the grinding has to serve your quality of life. It has to allow you to play (now and when you’re older).

Everything is play to me now. I only train in ways that I enjoy, like paddling, fat tire biking, hiking, lifting some weights, playing with my grandkids.

Effort: 10

Time: 3

These aren’t precise numbers. But here’s how I think about it

Fast twitch muscles are the most important for aging well. They allow us to generate force. They maintain bone density when activated and trained. They are the “youthful” muscle fibers, the ones that allow explosive movements. They’re also very rare and fleeting and disappear quickly, so they’re vital to train.

But they’re also the most dangerous things to train. Doing the sorts of movements at the sorts of intensities that maintain and develop fast twitch fibers will make you tired. Your muscles will be sore and you’ll feel the burn. If you do them in a fatigued state, and your form gets sloppy, you can get hurt.

What I tell people is to go hard as long as you’re feeling fresh. Higher frequency high intensity training without going to failure is my favorite way to train, particularly the older I get. There’s value in going to failure, too, but I’m not comfortable telling everyone to do that. It can go badly. But as long as you’re staying fresh and your movements are crisp, I see no reason not to push hard.

Alright. Til next time.