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How Does your Body Know You've Ate?

It sounds like a silly question, but I'm wondering. For example, diet advisors say to never skip breakfast. So what satisfies that requirement? A certain amont of calories? Volume? A mix of carbs/sweets/proteins that sparks a certain digestive response? Is is physiology, chemistry, psychological?

I can see how eating a big bowl of oatmeal, for example, will both fill the tummy and also require some long term digestion. But what if I have a glass of 2% milk and some yogurt? What about 2 glasses of water and a nutirtion bar? Are those too "weak" to bump the metabolism?

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    1. You beg the question whether some diet advisors are correct when they say that skipping breakfast is bad (for health, weight, or whatever). I believe that for weight-control it does not matter what time of day one eats one's food, so long as the number of calories ingested equals the number of calories expended.

      As for bumping the metabolism, it's been shown that hyperthermogenesis happens when one ingests a lot of calories at one sitting. The threshold for hyperthermogenesis varies among individuals and affects how efficient one's body is at keeping its weight stable. This was shown in a scientific experiment in which men were fed the same number of excess calories for a period of time. Some men gained a lot of weight, and some gained very little. There was a big range of weight gain, and the range was attributed to differing levels of hyperthermogenesis. Interestingly, the men who gained less weight tended to engage involuntarily in more fidgety movement after a big meal, such as jiggling the foot or restlessly getting up out of their seats, which burned off excess calories.

      I've been lucky to be one of those people whose body keeps its weight very stable, no matter what I eat. If I eat a meal, not even a very big one, my body soon feels like it's burning, especially the tops of my thighs. I get sweaty. Someone touches my skin and remarks how hot it feels. If I have gone hungry for an hour, I start feeling positively chilled; that's my body conserving energy.

      Google "thermoregulation" to read more.

      1. I follow Zone Diet recommendations. A meal should be comprised of a specific combination of protein, carbs, and fat. 40% calories from protein and 30% each from carbs and fat.

        Some feel that if too many carbs are ingested vs a balance of protein/carbs/fat, the body stores those carbs, as fat.

        A favorite breakfast is: 1.5 cups of fruit salad, 1/2 cup low fat cotttage cheese and several almonds. I tried processed bars and feel better (more alert) with home made meals.

        2% milk is close to being balanced, so are some yogurts, I like to give my stomach something to work on, adding a banana and a piece of turkey jerky to a glass of mik or some yogurt for breakfast would work for me.

        1. Insulin is produced by the body in order to convert carbs into usable energy. The connection between blood sugar and the release of that hormone must be part of the answer?

          1. i only feel that i've had breakfast after i've had a slice or two of good bread (loaf, not pre-packaged) with one of various protein condiments: almond butter, marinated white anchovies, eggs, swiss or goat cheese. my weight is maintained very well this way, cuts down on wild cravings during the day. bread people!
            oh, and coffee is a necessity. either plain demitasse coffee with sugar or with hot soymilk. the trick to your daily breakfast is to find the right amount of food. too much or too little and you'll feel tired.

            1. Leptin. The body secretes it and when this hormone reaches a certain level in the blood, the hypothalamus gets the message and says "Ah, satiety." That's when leptin is working as it should.

              2 Replies
              1. re: maria lorraine

                that's a very simplistic answer. leptin is but one factor involved.

                1. re: fara

                  Yep, simplistic answer. Care to elaborate on the other factors?

              2. As I recall from HS biology...(when we were carving in stone), fats, proteins and starches are processed by different means in digestion. Starches actually begin the breakdown into usable sugars for the body (as in blood sugar, those levels) in the chewing. I do recall a memorable Bio-lab experiement that involved a test tube of saliva. Lucky for me, I had a lab partner who would do anything to ge able to see my notes!

                So, ideally, for what I can figure, the point is to keep the blood sugar level at a good substained level...so balance of starches (fast), proteins (kick in more medium) and fats, (longer).

                Breakfast, seems most important, because in theory, we have fasted a night's sleep and we need to get that nice even working for the best blood sugar level back.

                But I am not a breafast person, so what do I know re theories? I think cold pizza is ideal. :)

                2 Replies
                1. re: Quine

                  This isn't in response just to you, but several have mentioned sugar/energy.

                  That seems a formula that can be cheated. For example, a cup of tea with 5 sugars. Would that trick the body into thinking it was nourished?

                  1. re: tastyjon

                    Not mine! I can't speak to all of the science here, but I know that my body responds to refined sugar in a way that's very different from its response to complex carbs or fats or proteins. If I had nothing but a tea with 5 sugars first thing, my blood sugar would soon tank and I'd have the shakes an hour or so later. I'd also feel faint and be unable to think straight!

                    My reaction might be more severe than some, but I'd think that everyone's body knows the difference, somehow, between substantial food and empty calories.

                2. Your body knows you've eaten when your brain has received adequate input from your digestive system that fuel has been introduced and put in process. That's how you and your body know you have eaten.

                  1. Major simplification following:
                    It has to do with blood glucose levels, body-produced insulin, and what kind glucose type you intake. Think of all food as glucose. Some things (5 packets of sugar) are broken down really quickly by the body because the cell structure of the "food" is relatively simple. A complex carbohydrate, on the other hand, well, just look at its name.
                    When the glucose intake doesn't meet the body's need for glucose, that's when the hypoglycemic sensations ("the shakes") begin.

                    1. You might enjoy this podcast on NY Public Radio
                      Hungry for More
                      Friday, April 13, 2007
                      On today’s Please Explain, a doctor and a food psychologist examine the physical and mental cues that tell us when, and how much, to eat


                      1. check out www.howstuffworks.com go to health then nutrition. Lots of answers for "silly" questions.

                        1. You want to start your day with around 300-400 calories.

                          If you eat processed or fast foods- it will essentially go right through you, and you will be starving a few hours later.

                          However, if you eat whole grains, an egg, fruits and all REAL food- it will take much longer for your body to breakdown and digest these foods, and you will not feel as hungry right away.