Our food has to much calories in it i think. its to easy to eat crap or put some toppings on or have a snack and you suddenly added hundreds of calories to your day.
When you eat refined sugars, they go directly into your blood stream, causing your blood sugar to spike. Your body deals with this by producing Insulin. This triggers your body to remove glucose from your blood by turning it into fat (and protein, and glycogen), and store it for later. It also suppresses your body's ability to release stored fat. [3] Each time you eat sugar, you body becomes physically incapable of burning fat. The more this happens, the more your body gets used to high levels of insulin (insulin resistance) which turns into Type II and eventually metabolic syndrome. [1, 2] The vast majority of Type II cases are dietary issues.
Your body has a well-defined hierarchy of what gets consumed first: (0) alcohol (1) carbohydrates (2) fats then last (3) proteins. [4] If you want to burn fat, you can't have carbs or alcohol around in meaningful quantities. Of the energy stores, dietary carbs are the only ones you don't need to survive -- your brain and red blood cells, I believe are the only part of you that requires them to live, and the liver/kidneys can synthesize all the glucose they need. [5] The rest of your body, including muscles, can operate solely on lipid metabolism. [6] In theory, anyways.
This, though, is the science behind Atkins and other fat/protein/ketosis based diets.
[1] https://www.hsph.harvard.edu/nutritionsource/carbohydrates/c...
[2] https://en.wikipedia.org/wiki/Metabolic_syndrome
[3] https://science.howstuffworks.com/life/cellular-microscopic/...
[4] https://www.myvmc.com/anatomy/metabolism-and-energetics/
[5] https://en.wikipedia.org/wiki/Gluconeogenesis
[6] https://www.huffingtonpost.ca/mike-sheridan/carbohydrates-an...
One example which I've used personally is https://store.bodyrecomposition.com/product/extreme-rapid-fa... . (Pubmed - https://www.ncbi.nlm.nih.gov/pubmed/24602091).
This would be an example where I'd argue the diet component (i.e. not eating) is much more important than the exercise component. Your BMR is ~2500kcal/day (10,000) and fat stores ~3500kcal, so fasting alone should account for 3 pounds of fat, and the 32 hours of exercise (low intensity, 330kcal/hr * 30hr = 10,000) the balance. This kind of math only works because you've got nothing coming in.
[1] https://leangains.com/fasted-training-for-superior-insulin-s... (and the many linked articles)
Admittedly, I saw no changes in weight until I hit about 20 miles per week when preparing for starting an actual training schedule. After around a 25 pound decrease, or ~30 to ~27 BMI, I think I'm closing in on my personal limit for weight loss without dietary changes or sacrificing more than I'd like to before the marathon, although I'm eating much more to sustain 40-50 miles per week.
At an estimate of 100 calories per mile [0], 20 miles per week is about 2,000 calories burned, and 50 miles per week adds up to 5,000. I find it difficult now to improve substantially without increasing calorie intake, but the weight loss just happens whenever I ignore nighttime hunger for 2 or 3 days a week during training. I ate the same amount or less without experiencing this hunger when I was heavier.
I wish I could offer some sort of source other than my anecdote. I can think of a few possible reasons why I'm not finding any data on this:
1. It's hard not to increase calorie intake while increasing exercise enough for weight loss to be noticeable. Based on my note above about only experiencing weight loss when I experienced mild hunger, it seems as though the same traditional calories in, calories out principle and the difficulties that come with that apply.
2. At the slower pace I've been running and that many who start off obese may run, it takes a lot of time to build up to the training volume necessary to experience weight loss. This may be difficult to replicate with a large enough number of individuals willing to participate in a study due to individual time constraints or job inflexibility.
3. This only works up to a certain point. I have not been successful in getting down to <25 BMI. BMI's an imperfect measure, but it aligns with my goals. I will be making dietary changes to decrease weight further, but intense exercise has been great for getting me started.
4. Not all calories are equal. I've learned a lot about nutrition since starting training and try to eat more foods that are high in iron. My diet is quite high in carbs, though, which most plans that don't require sacrificing calories do not recommend for weight loss.
5. It's possible that I've actually decreased my calorie intake without realizing it. I really doubt this. On Saturday to load up for a Sunday long run, I ate an entire small pizza, french fries, and tacos for dinner.
Does anyone else have similar experience with weight loss or have any sources that would advocate for high volume endurance exercise for weight loss?
[0] https://www.healthline.com/health/fitness-exercise/running-b...
Edited for grammar.
The adage about losing weight through "diet and exercise" is half lie. [2]
Don't get me wrong, you should exercise anyways, but don't expect to lose weight. That's on your diet.
[1] https://www.heart.org/en/healthy-living/fitness/fitness-basi...
[2] https://www.vox.com/2018/1/3/16845438/exercise-weight-loss-m...