You are correct on your above statement. Success is relative, and you're right about the "must" statement. When I say must, I mean that in order to be successful, you are most likely going to have to follow that type of regimen. Sure you can compete without doing it that way, and there may even be a select few that are able to do it successfully. As we all know, genetics play a huge role in this sport. Genetics may allow one person to achieve what another cannot through conventional methods (i.e. training style/methods, diet, drug protocol, etc.). You could also argue that taking AAS are not a must to compete, but let's face it, you won't be a real contender without it if you're competing on a national stage. I personally have not met one person, male or female, competing on the national stage that haven't used some sort of drug, and every one of them follow a frequent eating schedule. There is a reason behind it.
There has been consistent scientific research showing that people who eat consistent meals throughout the day, meaning 5 or more, are able to stay leaner than people who only consume 3. When your body goes without eating for several hours, it senses deprivation. As a result, your body has a multitude of responses. In no particular order, the following decrease: metabolic rate (to conserve energy), resting energy expenditure, thyroid hormone activity (T3). Frequent meals has also been shown to improve glucose tolerance, and serum insulin levels show a decrease of 25-30%. Decreased serum insulin leads to a decrease in lipase enzyme activity. Metabolism is shown to increase with frequent meals as well (diet induced thermogenesis, resting metabolic rate, protein metabolism). I will note that after consuming large meals, RMR spiked, but then dramatically decreased. In groups consuming more frequent meals, the increase was not as great, but was more consistent throughout the day. Frequent meals also show an increase in fat oxidation (measured by labeling fatty acids), carbohydrate oxidation, and reduced nitrogen loss (This increases when you eat protein. Retention is important for muscle preservation/building).
As a correlation, a couple factors increase as well. One of the hormones secreted by the gut is ghrelin. Basically just tells you that you're hungry, but aside from increasing appetite, it also slows down fat metabolization. During the absence of food, this hormone is increased. That hunger feeling you feel, is because of this hormone. Insulin is also negatively effected by reducing meal frequency. As we all know, I assume, insulin is a fat storage hormone. Also, individuals who consumed a small number of large meals/day showed significant increases in BP, total cholesterol, and LDL levels (in a particular study). Those who ate frequently showed decreases in the above biomarkers as well as C-reactive protein (responsible for inflammation).
Consistent and regular eating inhibit the above from occurring.
There have been numerous human studies on the above. Some dating back 50 years, although more accurate studies have been conducted recently. Some on your average person, some on overweight/obese persons, and on athletes as well. Studies based on consuming a small number of larger meals, show an increase in lipogenesis following meals, and an increased chance of obesity. Those who ate smaller, more frequent meals showed an increase in metabolic activity, and weight gain varied inversely.
There may be contradictory studies out there, but remember to consider the parameters of the study. What were they eating, how much, what is their body composition, what age group, was the total daily caloric intake hypo, or hypercaloric? Lot's of factors come into play, and changing just (1) variable can skew an entire study either way.
Some scientists even suggest that blood markers (BP, CPR, LDL, atherosclerotic plaque, plasma glucose, etc.) may improve with varying meal frequency, but there doesn't seem to be much information on the topic. I think a controlled clinical study on this topic would be very interesting.
I could keep going, but I would basically just be building on the above, unless I got into the chemistry of food and how it affects the body, and that's boring as ****. I am a science based guy, and trust in research and facts. Facts are, that there is enough scientific evidence to support that eating more frequent meals throughout the day is more beneficial than eating just 1-3. To be honest, if I wasn't a bodybuilder, and didn't compete, I would probable just eat 3/day, with maybe a snack in between. The reasons I eat the way I do are because of my lifestyle. Also, I get hungry, and because of assimilation. Your body can only metabolize a given number of carbs, protein, and fats per meal. What that number is varies by individual. The more muscle you have, the more you can take in without adverse effects (genetics does play a role in this as well). To eat only a couple meals a day doesn't mean you're WRONG, but it also doesn't mean that it's best suited for your goals. If you're serious about the sport, and want to IMPROVE, and build muscle, there is no way around the fact that you need to eat frequently, and take in the proper nutrients (macro and micro). Sure you can stay in good shape by eating your basic 3 meals, but are you getting all the macros you should? Why not take every advantage you have in order to improve? Eating properly, and frequently, is one of the most simple things you can do to improve your lifestyle, health, body, performance etc. For maintenance, sure, you can just eat a couple times a day and be fine. For many people, this would be adequate. But for most of us, I think optimizing our potential is a high priority. I can only assume, since we are all members of a bodybuilding forum. We may all have different goals, but I think it's safe to say that health and fitness is a lifestyle we all enjoy, whether we compete or not. Let's make the most of it! But to each their own...
Lastly...Did the supplement industry try to preach this in order to make a profit? Probably. But this doesn't negate the fact that bodybuilders have been eating this way virtually since the sport began. Dietary supplements (i.e. protein powders, weight gainers, MR shakes etc.) weren't always around. I believe that they did capitalize on the opportunity in order to make profits though. Good business practice, but I don't think it's all BS.
*If I missed a topic, want me to go deeper (that's what she said. haha), or you have a question, ask (nicely lol). I'll be happy to answer if I can. I'm not here to get into a pissing match. Just want to spread the knowledge. I would have posted this first if I had time, but as you can see, it's not a simple answer, and I do get busy, as I'm sure most of you do as well.