Michael Phelps ate 8,000 – 10,000 calories a day

The diet of former competitive swimmer Michael Phelps went viral during the 2008 Beijing Olympic Games. He ate 8,000 – 10,000 calories a day to fuel his activity. 

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Sefa Kozan
April 25, 2021 10:13 pm

As a certified personal trainer, I remember clearly when Michael Phelps’ unbelievable diet went viral in 2008. You have to remember back then the general public’s grasp of nutrition wasn’t as strong as it is now. Though sometimes I hear about a new fad diet and think we’ve gone back 20 years – but that’s another story.

Back in 2008 we put foods in two categories. They were either ‘clean’ or ‘dirty’. The criteria that was needed to be clean or dirty weren’t very clear. Generally fruits, vegetables, whole grains and lean meats were considered clean. Junk and fast foods were considered dirty. Nutritionists at the time were trying to set people straight that categorizing foods like this wasn’t helpful, but traditional thinking prevailed. It was thought that if you ate clean foods, it didn’t matter how much you ate, you would still lose fat. Conversely it was also believed that if you were eating clean foods and then you took even a small bite of a dirty food, for example a cookie, then your fat loss progress would be ruined.

In hindsight it was quite silly – as most things are when you look back at them with the knowledge you have over 12 years later. So when news of Michael Phelps’ diet broke, it led to a lot of confusion. Here’s a guy who’s eating pizza, meatballs subs and energy drinks, but he’s ripped! He’s eating dirty foods but he’s in shape. How does that work? Even more so, he’s an Olympian. Arguably the greatest Olympian ever. So his performance didn’t suffer by any means.

I would put down this viral event as an integral part in changing the way people think about weight loss today. Before it was about clean and dirty foods. But knowing that Michael Phelps could eat up to 10,000 calories per day, a lot of them labelled as dirty calories, and burn them off as part of his intense swimming practice made many people realise that energy balance was they key. We soon learned that weight loss wasn’t some complicated mystery. You didn’t have to possess some fat loss secret that you see someone trying to sell on a YouTube ad. So thank you to Michael Phelps. He may not know it, but he’s had a bigger impact on the public’s understanding of nutrition than he gets credit for.

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Travis Banks
April 27, 2021 10:20 pm

How many times have you heard someone say “I can eat what I want. I’ll burn it off later”? I agree with that our understanding of dieting and nutrition was fractured in 2008. But it’s still fractured. In the United States we have been trying to tackle obesity for decades but failing miserably. 73.6% of adults aged 20 or over are overweight and obesity can incur medical costs of up to $147 billion each year.

Michael Phelps’s hypocaloric diet can be positive depending on how it is interpreted. If it helps you better understand the calorie-in, calorie-out model, then that’s great. But if it makes you think you can eat whatever you want and just burn it off later, then that’s problematic.

Eating what you want and then burning it off later works. Michael Phelps showed this to be true. But unless you are an Olympic-level athlete, you probably won’t get away with stuffing yourself with pizza, milkshakes and burgers. That jog in the park after an indulgent lunch will hardly make a dent.

These are some common exercise activities for 30 minutes for a 155lbs person, and their corresponding caloric expenditure [Source: Harvard Medical School]:

  • Tennis: 252 calories burned
  • Running (5 mph): 288 calories burned
  • Yoga: 144 calories burned
  • Walking: 133 calories
  • Cycling (12-13.9 mph): 288 calories burned

As you can see the caloric expenditure for everyday exercises isn’t huge. Of course, greater intensity and duration will increase the calories burned. However it’s humbling to know that your 30 minute tennis game can be undone by just one Snickers bar. This small fact alone confirms that life is unfair!

The good news is that Michael Phelps didn’t burn all of those 8,000 – 10,000 calories from his exercise activity alone. Digestion burns calories. Everyday bodily processes burn calories too; the total amount is known as your Basal Metabolic Rate. Your BMR tends to be higher the more you weigh, in particular the more muscle mass you have. So if you really are craving that Snickers bar, you don’t have to play a 30 minute tennis game to burn it off.

Ironically the diet of Michael Phelps, which was one of the most extreme diets I had heard of, taught me that moderation is important. I can enjoy some of my favorite foods with the comfort of knowing it can be burned off, but it also showed me how much activity needs to be done if I’m looking to burn off high calories foods like pizza and ice cream.

Abi Ortega
April 30, 2021 10:19 pm

I’ve always wondered where these gigantic calorie challenges originated from. Calorie challenges are a dime a dozen nowadays. It is a good way to get views, naturally encouraging content creators of all types to give it a go. But where did it start?

Competitive eating has been around for decades. The first recorded pie eating contest took place in 1878 in Toronto. But taking an educated guess we can almost be certain that contests involving food consumption have taken place throughout history, way before 1878. How about internet history?

Well it appears that calorie challenges first started appearing on YouTube soon after Michael Phelps’s 10k calorie diet got some media exposure. Athletes have been eating lots of food way before the Michael Phelps diet was even a thing. But the media exposure and racking up of gold medal after gold medal put his diet in the limelight. It is soon after that you see calorie challenges appearing.

It is not a giant leap to say that Michael Phelps’s diet during the 2008 Olympics gave birth to the viral internet trend of calorie challenges. Taking this one step further, we can also posit that the PR surrounding his diet created interest that would later be taken up by the Mukbang genre; a genre of video in which content creators eat food while interacting with their viewers.

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Russell Bumak
April 28, 2021 11:13 pm

For an active professional athlete, eating is a full time job. Although eating 8k-10k calories a day sounds like an enviable position to be in, I can assure you it is not fun or pleasant when it’s your job and you’re not hungry.

A common theme for high performing athletes is the difficulty to transition to everyday life after spending the better part of their life living the athlete lifestyle. This doesn’t mean just being out of the spotlight and no longer being in a competitive environment. It also affects their diet. Some athletes like Michael Phelps have to consume huge amounts of calories to sustain their activity. But once they retire, their diet often remains the same and their activity levels aren’t able to keep up.

This happened to Michael Phelps. He gained 30lbs after retiring. A combination of less activity without cutting down on his calories. It might sound very simple to do. You’re already eating huge amounts. How hard can it be to eat a little less? Not so easy. When you’ve been doing something for years, your body goes on auto-pilot mode. You can’t just switch off your eating habits like a light switch. It takes time.

Interestingly for some athletes such as NFL players, the opposite happens. Offensive linemen can be 300lbs plus. Over the decades they have been getting bigger and bigger. And in order to maintain this size, they need to eat a lot! Some NFL players have opened up about the pressure to eat, talking about how they would get in trouble with management if they missed a meal and lost some weight. Taking medications to alleviate stomach pains at night shows the lengths these athletes have to go to maintain their enormous size. You may be an athlete but there is nothing healthy about that.

But once they retire they no longer have the pressure to eat as much as they once did. Without even monitoring their food intake and just eating normally, former NFL athletes have lost up to 60lbs of weight and look totally different after a few months of retirement. It’s a stark contrast to those who continue eating like they are athletes without the corresponding activity.

Nicole Stratton
April 26, 2021 4:11 pm

If you go back and read the articles that published the diet of Michael Phelps, a lot of them have one thing in common. They recommend NOT to follow his diet 😅 I can imagine the excitement some people would have felt. “Wait a minute. I can eat all that and still stay slim? Sign me up!” Well, unless your entire life revolves around eating, sleeping and swimming, it’s unlikely to work for you.

Phelps would train 5 hours a day, 6 days a week. He would eat 5 times the recommended daily calorie amount for a man. But this isn’t too far-fetched when you recognize he was training 5 times the amount of a regular gym-goer. To put this into perspective, there is another sport where athletes eat up to 10,000 calories a day. Sumo wrestling.

Sumo wrestling undoubtedly involves activity. But it’s more of a stop-start nature. Short bursts of activity, followed by rest. Its anaerobic nature, compared to swimming’s aerobic nature, results in a very different body composition. Sumo wrestlers hold much more muscle and fat, which are both helpful in pushing an opponent out of a dohyō and resisting their pushing and grappling. Swimmers hold less muscle and fat than sumo wrestlers. They don’t have to contend with an opponent tugging and pushing them. Aside from a sprint race, swimmers also focus on improving their endurance in the water.

10,000 calories for a swimmer and sumo wrestler result in vastly different outcomes, determined on their activity levels and training styles. So if you are thinking of taking in 10,000 calories a day, make sure your training is appropriate for it!