I think that if they are eating one meal per day, and 0 carb, that their bodies are FULLY adjusted to ketosis and fat burning and their metabolism has adjusted as well. IMO this is extreme from a traditional 3/4 meals a day routine. However, its not that extreme for someone who is adjusted to Ketosis on a 3/4 meal per day routine as your macro #s are different. Since its ALL ABOUT protein/fat ratio and total amounts.

Id say if you want to try this there is an order to be followed: SAD -> Paleo -> LC Paleo -> VLC Paleo -> No Carb Paleo(Ketogenic) -> 3 week adjustment period -> IF w 3 meals -> IF w 2 meals -> IF w 1 meal (Intermittent fasting with 1 meal/24hrs) <--If you want to do 1 meal no carb IMO I wouldn't recommend it.

Also, don't believe everything you read or hear. Many of the 'I eat 1X a day' people use Meal Replacement Shakes and/or 50+ gram protein shakes multiple times a day. Someone who eats solid food 1 time per day but drinks 150 grams of protein a day is really 'eating' FOUR meals per day.

You're probably takig him literally. I know a ton of people who say they eat one meal a day. What they really mean is they eat very little breakfast or lunch and then eat one large meal for dinner. That's usually what they mean. They may snack on yams, eat cereals with milk, or yesterday's leftovers for breakfast -- to them, that's not really a meal, since it wasn't really prepared Or lunch may be a protein shake or even an egg salad sancwich, an apple, and a box of Johnnie crackers.

When we say we're eating a meal, we mean sitting down and eating a prepared meal with appetizers and main course, and dessert. At least, that's what most people mean. Don't take it literally unless these guys are counting calories, tracking macronutrients and checking their micronutrients and minerals like some people do around here.

From the Ironman article linked above:

LT: You mean actual food, right? I’m sure you take in meal replacements. . . . GP: Yes, I’m sponsored by Met-Rx; I really like their products. Being a sponsored athlete, I have a plethora of them on hand. I drink their RTD-51 protein shakes. I use the Amped RTD for energy before every single workout. I also use their glutamine and NO2 pills, their fat burners and stuff.

So he drinks Amped RTD every morning too, besides the one meal a day. I don't see how he couldn't: the guy goes non-stop all day, strength training in the mornings, career during the day, cardio at night.

I have been eating one meal a day for a couple of weeks, except Xmas with family. I started LC and then paleo with dairy and then without dairy. My carbs now are around 50g/day. I accidentally missed meals after going LC, and decided to try IF. I first skipped breakfast, then ate 2/day with a late lunch. Now I eat in a 3 to 5 hour window in the evening. I only take in water or green tea while fasting. I do this because I feel great when I do. I am still overweight by more than 50 pounds, but I'm not motivated by weight loss. Rather, I like how I feel. On the few days when I did eat a breakfast, I felt less well. I suspect this is easier to do when you are older. I am 48. I also exercise vigorously only about once a week. The surprising thing is that I'm not hungry, even after 18 to 20 hours.

Yes, I have tried this before. It is just another type of fasting protocol. Here is a link to a fitness model/bodybuilder who also does the one meal a day thing.

http://www.ironmanmagazine.com/site/greg-plitt/

This kind of eating can also have different names such as ESE (Eat Stop Eat) or PSMF (Protein Sparing Modified Fast). I might do this only one day a week though. I usually do two meals a day as per Leain Gains protocol.

I have tried this. I literally only ate between 5pm and 7pm every day for about two weeks.

The only change I noticed was a slightly bloated feeling in the mornings.

It's worth noting that I was transitioning away from 2 meals a day.

I am 43 and I have a sit down job. You must weigh in ALL factors before taking off on someone's personal diet. It is PERSONAL. Ok enough. I eat one large complex carb & legume meal at night. I wakeup and have veggie and protein shake then hit the gym. I then don't eat anything for the rest of the day except very small snacks like a small pinch of seeds or a sip of protein and veggies. Because I work on the computer all day I find if I don't have food during the day I don't fall asleep at my desk. By the time I eat my huge meal at night I have the digestive fire roaring. This is much what our genetics are designed for. Work hard morning through til night fat n' happy and sleep. It's so much fun. Once you understand the hunger pains are really your body craving carbs/sugar it is easier. It seems uncomfortable to do this every day but it's worth it. Basically it is like going from carb to fat burning every day. I mean if you believe in God then you must believe that he designed our bodies to be very efficient right? I just can't buy that I have to eat morning, day and night 3 course meals. What would happen to grocery stores, restaurants and all of the other businesses built on stuffing us morning, day and night? What if we could thrive with just 1 large meal a day with very light snacking morning and day? Now if you have an active work profession like construction you could not do this. However many people sit at desks. You have to tailor diet to your own personal lifestyle and genetics. I use beef, whey and egg white isolates. I balance these with fresh blended spinach and spring mix (digests more easily than other high cellulose greens). I typically wake up with a ph of 5-6. I then shoot for ph 7. ph balance is key. Also I don't use any grains, sugar and limited fruit. This allows me to bounce between keto and carb very easily. Bottom line is you really need to study to become your own health expert.

I've tried this a few times. Wonderful not to have to carry lunch. Eating enough food at once was a bit of a problem. The other problem is that humans are social creatures, and they usually like to socialize right about when I would want to be eating.
A few carbs don't necessarily hurt your chances either. Sleeping for eight hours is a fast itself and can put you back in ketosis by morning.

Yes is works! I'm on it now, but probably not for or in spite of any reason people seem to offer. Yes, humans did evolve to eat sporadically, but we also evolved to die young. So what conclusions can be made.... None, and you know what? That's just fine. We need to be ok when answers are not readily available. If we aren't, people will just makeup sensible sounding explanations like "fuel" and "metabolic rates". These are so grossly deceptive that they do a huge disservice to people actually trying to lose weight or get in shape.

The truth is we don't really study diet....or at least not anything like how we study pharma. There is no money in it, and the field is already full of quacks and personal trainers that will say whatever they have to so that you don't ask if they have a degree in anything other than fitness magazines. They are well intentioned, but not informative. Diet studies are particularly hard to do because they are so intrusive if done correctly. Study participants have to stay in the experimenters facilities for months in order to exclude the possibility that they deviate from the study protocol. Because of this, most studies are done epidemiologically, meaning through surveys. Respondents to surveys have dreadfully different experiences than average people, potentially throwing out anything useful in the data.

Again, I don't know why it's worked for me. I can tell you my own personal experience, one you might not share. I started doing a 1 meal a day plan 5 days a week. At first it was hard, I'd get hungry and cranky, but after a few days, all that went away. I find that it is difficult (though not impossible) to eat more calories in one meal than I otherwise would have in 3. I have lost weight, I work longer hours (no lunch break), and am losing weight at a steady pace. If I wanted to lose some more quickly, I could eat diet food for my one meal. But I don't, at least not yet.

Moral of my story is that 6 meals, 3 meals, 1 meal....doesn't matter as long as you are reducing your caloric input. Yes there are some other factors such as metabolism, but on the whole, they represent such a small fraction of the variance in diets (1-2%), that making that your guiding principal is arguing over crumbs. If you are diabetic, or have immune problems, check with your doctor before trying anything. Otherwise try it, you may like it.

Please no more nonsense science. If studies are published by reputable journals, make sure you convey their significance rather than speaking in themes. And stop pretending that you know something that you don't. I want you all to remember that there REALLY are people out there that work hard in real science to find out certain truths who will always be shouted down by the ignorant and the self invested.

Not sure I could ever do that. Wouldn't it be bad for your metabolism to starve yourself all day and then eat between 5-7pm?

I also have hypoglycemia & hypothyroidism and am supposed to eat 5-6 times a day. I find I'm ALWAYS hungry, except if I'm in ketosis, then I'm less hungry but still hungry often. Sigh

I asked Tait Fletcher how he pushes through CrossFit while staying Bulletproof. He said he only eats one meal a day and supplements with the fat-filled coffee the rest of the time.

That guy's about as jacked as a person can get, so I'm gunna give it a shot...