The Role of Diet vs. Exercise in the Obesity Epidemic

The Role of Diet vs. Exercise in the Obesity Epidemic

When it comes to obesity, which is more important: diet vs. exercise? Can weight be lost without exercise? The common explanations for the cause of the obesity epidemic put forward by the food industry and policymakers, such as inactivity or a lack of willpower, are not only wrong, but actively harmful fallacies.

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When I sat down to write How Not to Diet ( I knew this “what triggered the obesity epidemic” was going to be a big question I had to face. Was it inactivity—just kids sitting around playing video games? Was it genetic? Was it epigenetic—something turning our fat genes on? Or was it just the food? Were we eating more fat all of the sudden, more carbs? More processed foods? Or were we just eating more period, because of bigger serving sizes or just snacking more? Inquiring minds wanted to know.

This is the first in an 11-video series to answer this question, which I originally released in a 2-hour webinar earlier this year. If you can’t wait and want to get all of the videos at once, check out the webinar digital download here (

Or, just stay tuned for the rest of the series (note that each link will be live when that video is published over the next few weeks):
• The Role of Genes in the Obesity Epidemic (
• The Thrifty Gene Theory: Survival of the Fattest (
• Cut the Calorie-Rich-And-Processed Foods (
• The Role of Processed Foods in the Obesity Epidemic (
• The Role of Taxpayer Subsidies in the Obesity Epidemic (
• The Role of Marketing in the Obesity Epidemic (
• The Role of Food Advertisements in the Obesity Epidemic (
• The Role of Personal Responsibility in the Obesity Epidemic (
• The Role of Corporate Influence in the Obesity Epidemic (
• The Role of the Toxic Food Environment in the Obesity Epidemic (

Have a question about this video? Leave it in the comment section at and someone on the team will try to answer it.

Want to get a list of links to all the scientific sources used in this video? Click on Sources Cited at You’ll also find a transcript and acknowledgements for the video, my blog and speaking tour schedule, and an easy way to search (by translated language even) through our videos spanning more than 2,000 health topics.

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Thanks for watching. I hope you’ll join in the evidence-based nutrition revolution!
-Michael Greger, MD FACLM

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  1. my kids are pretty thin and it’s probably because i don’t support fast food. they eat a lot, and even some junkfood at home. We eat a lot of beans and homemade soups with beans consistently. I was an overweight teen, and we ate fast food almost everyday. It’s amazing that just cutting that out of their life has had such positive results. It’s fast and easy to make minestrone soup, bean burritos, scrambled tofu etcetera.

  2. Love your work. Boring question – who edits these videos? I am about to create 30 or so on a different topic and love this style.

  3. It was also the time period when major food companies started adding appetite stimulating chemicals to their processed foods.

  4. About 50 years ago the Food Pyramid, emphasizing carbs (potatoes, wheat, beans and other plant-based products) over meat, while at the same time cultivating a baseless phobia of saturated fats and dietary cholesterol (like butter, bacon and eggs) was introduced by the FDA. Over the next few years that bogus Pyramid was adopted by the rest of the world. It has nothing to do with calories. I can eat 2000 calories/day and still lose weight as long as I don’t eat carbs.

  5. I can eat healthy and exercise and still gain weight. Low fat does not mean low calories, stomach volume works against me 😑

  6. Hmmm. In my limited experience the easiest way to lose weight is through consistent low level exercise over an extended period of time, you know kind of like what hunter gatherers did, the modern lifestyle with excessive sedentaryness has always appeared to me to be 90% of the problem. I guess when they do research they’d be hard pressed to find a comparison group…

    Sleep was not mentioned here, poor sleeping habits is likely another contributor.

  7. Dr. Greger, yes nutrition is more important that exercise although exercise is important, please exercise more to inspire more ppl that mostly plants is the way, thanks.

  8. This makes so much sense!!! Also a lot of the time people eat foods that have a lot of calories but don’t make you feel full like whole plant foods do!

  9. Im eating only what dr Greger says and I’m exercising (well not as much as he says. Like 20 minutes a day) and I’m always 3 kilos heavier than I should be. What can I do to lose these 3 kilos without losing nutrition my body needs? If I eat less, cronometer shows I dont get enough iron and calcium. And I’m eating 2000 kcal every day. I’m 1,64 kg and I weigh 59,5 kilos. Should I eat less calories? If i run everyday 45 minutes I become too muskular. Also now it isn’t easy to do as much exercise. I live in Greece and we are in complete lockdown. We are only allowed to run around our neighborhood .45 minutes running in circles is not what somebody wants to do. I eat all the nutrition dense food. At least I think so… is there any way to become thinner? It would make me happy. Since I’m vegan firstly I became thinner but now I don’t seem to lose weight and I will never go back to eat a non vegan diet. Thank you…

  10. You’re a charlatan. Not a doctor, or a scientist. Anyone who claims that fat causes insulin resistance, should be punched in the face and jailed.

  11. The obesity epidemic, two cold showers per day ,counselling 2hrs per week , meditation 2hrs per day this helps

  12. Ya see guys and gals not this "Corona Virus", but ‘Obesity’ etc is the likes of theme real "Pandemics"…

  13. Love your work. Boring question – who edits these videos? I am about to create 30 or so on a different topic and love this style.

  14. ive started adding "healthy fats" to my diet via chia, flax and hemp seeds and been eating brazil nuts for selenium and mixed nuts and also pepitas everyday for zinc and ive never put on so much weight so fast in my life, i came from a mcdougal style diet and was convinced that fatness was only caused by saturated fat but i now know ALL fats make me fat, (i think i discovered why you are always on a treadmill!) if its not the nuts and needs it must the stress of having to worry so much about getting individual nutrients, caused me a mid life crisis

  15. I thought you were going to implicate the governments role in getting cheese products sold to restaurant chains.

  16. Louis le Gros was corpulent and other aristocrats, but also the members of the highest clergymen of the catholic church.

  17. I was disappointed to see the updated version of Biggest Loser still emphasized ridiculous levels of exercise for extremely obese people while never addressing diet at all. At least Dr Now on 600 lb Life tells his patients exercise doesn’t really increase weight loss.

  18. Dr. Gregor with all your knowledge of the truth and statistics and all the rest why are you not coming against the coronavirus so called pandemic you know as well as many other doctors the numbers don’t match the hype and the shut down of our country you guys watch Pam popper or Dr. Bergman they say it straight

  19. Dear lower body temperature in vegans a thing?I thought I heard that somewhere in an article about normal body temperature.I am not able to find any solid info one way or the other.Just asking due to recent events.Thank you for helping so many live better lives

  20. Wow! This was very eye-opening – especially the part about fast-food industries trying to emphasise exercise instead of reducing calories. Thank you!

  21. This video should be widely distributed and shared, it is eye opener to how food and beverage industry deceive consumers

  22. The zoonotic virus epidemics and pandemics also started to increase dramatically since the late 70’s, right? Can’t be a coincidence, it is proof of what is so wrong about our world, our lives today.

  23. All I heard growing up was “drink three glasses of milk and eat all the bread you want.” We feed our kids like livestock and wonder why they’re getting fat.

  24. I know this is true because once I switched from SAD to a plant based whole foods diet I dropped weight whether I exercised or not – and believe it or not, it was about the same amount of weight either way.

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