"I'm not hungry, it's after dinner, and I worked out, do I still need to eat the extra calories?"
And there are almost always 2 very separate and distinct thoughts on this.
I would like to clear up how it's geared to work if you follow MFP's recommendations explicitly.
Just so we have a solid starting point, let’s assume that the person in question has done the goals wizard
and put in the correct information and chosen an appropriate goal for weekly weight loss (not always true, but we have to start somewhere).
With the above statement as a given, the two opinions are basically:
1) Eat them, always.
2) If you're not hungry, don't eat or "Listen to your body."
Before we go any further, I'd like to detail how the human body normally registers hunger and how that normal process can become distorted in people who are unhealthy.
For people who are at a healthy weight, and have no metabolic conditions, and who eat generally healthy, hunger is a sign of energy need. When you need energy, your body sends out signals in the form of hormones that trigger the brain to say "feed me!” . The two main hormones affecting hunger levels are Ghrelin and Leptin. Ghrelin is a short term, "feed me now" hormone that governs our immediate desire for food, whereas Leptin is a longer term satiety response to feeding. These two hormones work in concert to each other. When healthy, the hormones are sent out at the correct times and in the correct amounts based on how much energy is needed.
The first argument (Eat them, always)
Studies done on these hormones suggest that in obese people, the central nervous system may become desensitized to the Leptin response (RE: Roles of Leptin and Ghrelin in the Loss of Body Weight Caused by a Low Fat, High Carbohydrate Diet" - The Journal of Clinical Endocrinology & Metabolism 88(4):1577–1586 ).
Research is unclear as yet as to the exact cause of the insensitivity to these hormones, but the outcome is the same, essentially in many obese people, hormones are incorrectly interpreted. This means that for those of you (myself included in the past) who aren't considered to be at a "normal" or "healthy" weight (I.E. obese) may not be receiving the correct signals about when to eat, when not to eat, and how much to eat to satiate your hunger levels.
That means you should be relying on our higher brain function to figure out when to eat and when not to eat. Eventually, your body will correct the hormone insensitivity, but until that occurs, it's not accurate to say that your body knows when it needs energy.
The second argument (eat when you are hungry).
This works if you're generally healthy, but only to a degree. If weight loss has been an issue in your past, many times eating is a psychological "control" issue, and thus even if our body is physically sending out certain levels of hormones, your brain could be either masking those hormone levels and/or heightening the sensitivity to those levels subconsciously in order to satisfy some primal response to trauma in your life. At least until you can confirm that your body is correctly signaling for food, you should be very aware of when you feel hungry, and how much you are eating before you feel full.
It boils down to this: You can't just "eat when you're hungry", you must make sure, first, that your body is correctly telling you when to eat and how much, and until you can confirm that, you should NOT trust those signals.
The question then becomes: How do I eat those extra calories.
It's actually not that difficult, but it takes practice. You must do some prep work ahead of time, if you know you're going to be exercising on a given day, estimate how much, and add extra calories throughout the day, don't try to stuff yourself at the end of the day, after a few weeks of this, it's not that difficult to do, but you do have to actively practice it or it won't work. Make it a habit, that's the easiest way to do it.
Hope this helps people out there.