I like to keep a latish schedule, sleeping often around 2-3 AM, I'm often eating odds and ends late at night. If someone eats Meals A, B & C of certain calorie content, and then timeshifts his schedule so that he's eating the same meals later at night, and closer to when he's about to sleep, will he gain "excess" weight? If so, why?
- It takes 6 hours from the last carb you ate for your pancreas to switch from producing insulin to producing glucogon. Glucogon is a fat burning hormone, and is designed to maintain a minimum blood sugar, and converts fat to sugar. It's the opposite of insulin which is designed to maintain a maximum blood sugar and traps excess sugar as fat.
- Your pancreas is designed to have cycles of producing insulin and glucogon.
The most common time when we have more than six hours between meals is when we sleep. If we get the suggested 8 hours of sleep, and we eat carbs right before bed, you'll only have had 2 hours of glucogon production. To improve your body's performance, you may want to delay breakfast.
If you have several small meals 3 hours apart, and all contain some form of carb, your body will be producing insulin the majority of the day. Remember, it's designed to have cycles of insulin and glucogon production.
If you have those same small meals 3 hours apart, but only two contain carbs (breakfast and dinner), your body will switch over to producing glucogon in the middle of the day as well.
One of the reasons that many diets suggest no meals within 4 hours of bed time is that two hours after you sleep your body is starting to burn fat. That gives at least 6 hours of fat burning at night, and more if you eat an hour or more after you get up.
In the vast majority of cases, it doesn't matter when you eat. What matters is what you eat and how much of it. If you take in more calories than you spend, you gain weight. If you take in fewer, you loose weight.
With this said, you need to find a method that is sustainable for you. Most diets fail because people can't sustain the effort. So it's critical to find the method (to limit calories) which is the least difficult for you to follow.
It's likely that some people find it harder to exercise moderation at night, especially in a fatigued state. Therefore they might find themselves overeating at 10pm when they would have eaten smaller amounts earlier in the day. It's also possible that the kind of food you go to at night be more conducive to a high caloric load (e.g., "snacks", highly palatable fat and/or sweet foods, nuts, etc).
For those people it might be beneficial to simply not eat to much at night. Others will do better on a low carb or low fat diet (either of which can result in lower calories intake), or by a strategy of having multiple small meals each day, or fasting, etc, etc.
The hormonal changes induced by the type of food you eat or your timing might have an impact for some people some of the time at the margin, but the research is very spotty on that. In the best of cases, they only matter for small refinements, but not for an everyday approach to loosing weight. In short, they might be relevant to elite athletes trying to "make weight", and training on the bleeding edge.
Your body has to convert calories to something it can use, whether that be glucose or fat.
If calories are converted to glucose, your body is going to burn it off (or it goes to the toilet).
When calories are stored as fat, it takes longer for your body to access that energy because it now has to convert stored fat to glucose. This makes a person feel tired.
Eating before bed is going to result in more calories being stored as fat because the body does not need that energy while in shutdown mode.
If your body burns 2000 calories a day and you eat 2000 calories a day, eating shortly before bed will result in you feeling more sluggish during the day.
If you take in 2000 calories a day now and you made it a point to take in that fuel early enough for your body to process more of it into glucose, you are likely to burn more than 2000 calories.
If I eat at 6 PM and go to bed at 9 PM, that should be equivalent to you eating at 10 PM and going to bed at 1 AM.
Of course it does!
If you eat late at night, and then sleep, your body does not use up the energy taken in. So your body converts it into fat. (how much fats are produced depends on how much carbs you ate). So make sure you eat your heavy meals during the day - not at the end of it!
But of course this depends on other factors (what is explained above is for normal people). Some people have a high metabolism so they don't save up lots of fat.
In my opinion, it is just better to stay away from eating at night.
My claim: Night eating by itself does result in more weight gain than daytime eating. Night eating often means you eat something additional, more than you need, which can result in weight gain.
Study 1. Night eating and weight change in middle-aged men and women. Pubmed
Night eating was not associated with later weight gain, except among already obese women, suggesting that getting up at night to eat may be a contributor to further weight gain among the obese.
Study 2. The night-eating syndrome and obesity. Pubmed
Night eating syndrome does not always lead to weight gain...
He can gain excess because of insulin. And of course the way insulin works has been exploited by bodybuilders seeking to increase muscle mass. So where one wishing to reduce their weight may want to eat their last meal several hours prior to entering REM sleep, a bodybuilder may actually consume two pre-retirment meals (setting an alarm clock four hours in to a rest period to get another protein window)