Yes. The feeling of fullness is produced through a combination of hormone signalling and good old fashioned eyesight (and probably some other things I don't know about!).

Hormone signalling is linked to your metabolism, so screwing this over by yo-yo dieting, lack of sleep, eating processed foods with plenty of delightful additives etc. can deal with this. This could, though, lead to health issues down the road.

Eyesight... now that's an interesting one. Basically hormone signalling is kinda slow, so the brain augments this by eyeballing how much you are eating and guessing at when you're full. There was a study years ago (sorry, I don't have the link) where they got students to eat soup and then stop when they were full. Half the group had to refill their soup bowls themselves, but the other half (unbeknownst to them) had their bowls automatically refilled by a hidden pipe. The former group got full after a bowl or two or soup, but the latter group ate something absurd like a gallon of soup before they felt full. All because the brain didn't realise how much they were consuming.

So it's perfectly possible to get around feelings of fullness, at least to an extent, by 'tricking' yourself. This is mindless eating - watching TV whilst eating, for example - anything that distracts you so that your brain doesn't clock how much you're consuming.

You could also boost your appetite through exercise. This is probably not going to help you gain a lot of weight, but it will make the process healthier.

I think the current answer is "we don't know". There haven't been many studies on the subject, but those that have been conducted seem to indicate that there may be a counter-intuitive link between diet soda and weight gain.

One observational study demonstrated a correlation between increased diet soda consumption and weight gain. Correlation isn't causation, of course, let alone an indicator of what mechanism may be behind it. For example, it is one thing if people are substituting regular soda for diet soda (that would be counter intuitive), but the result would make a lot more sense if people were drinking diet soda instead of water.

Possible causes for the effects observed include:

- Artificial sweeteners drive greater sugar cravings rather than satiate them, i.e. diet soda doesn't make you fat itself, but drives changes in diet that do.

- Artificial sweeteners directly damage metabolism, leading to subsequent weight gain.

A 2008 study, which controlled for diet, exercise and other factors, looked at a variety of factors which affected incidence of metabolic syndrome. A "Western style" diet was associated with an 18% increased risk, but diet soda came out on top with 34%.

Another study looked to control for eating habits, and found that participants people who consumed more artificial sweeteners gained more weight, but only an average of 2 lbs over the course of a year.

Lastly, a study on mice adds credence to the idea that artificial sweeteners themselves are the direct cause of weight gain. Rats were put into two groups, each of which has access to as much food as they liked. One group was given artificial sweeteners on top of this. This group ate the same as the control group (indicating that sweeteners don't induce cravings) but gained more weight.

So it would appear that diet soda doesn't boost appetite, but that artificial sweeteners themselves could induce weight gain through metabolic damage. But these are small, sparse studies (and one isn't even on humans!) so it is difficult to draw concrete conclusions.

I went along to a pub meet in London and people kept asking me what my screen name was. I said I was hardly ever on the forums so it was almost irrelevant what my name was... I kinda liked it so I changed my name to this!

I'll assume you're not looking for a gender-specific viewpoint and chime in.

I'm in decent shape and like to think I have a healthy relationship with food. Some would probably say I'm a bit too strict with what I eat, but whilst I like to control what goes in my mouth I've never had any clinical/psychological issues with food. My strictness isn't driven by a desire for control, but because I have a relatively slow metabolism and frankly just can't get away with eating crap.

I've never remotely considered that this strictness with food is related to being a feeder. For me that's just a sexual quirk/fetish that otherwise doesn't inform my life or vice versa.

The two things do clash, though. What may have personally started out for me as a vanity thing has matured into a matter of health. I believe that humans are incredibly versatile and athletic physical animals, capable of moving in an extraordinarily diverse and beautiful manner. Just look at gymnasts, parkour etc. This is what I want for myself, and yet what turns me on is women gaining weight. It's a frustrating dichotomy that I have yet to resolve.

From an erotic point of view I can see the appeal of an out of shape woman, although I'm not that fussed either way.

But from a practical and moral standpoint, I'm strongly in favour of in shape. I know framing it in terms of morals is a bit dangerous, but basically I think that having a decent level of fitness is very important to health and quality of life, particularly as we get older. I'd very much want those things for anyone I care about.

Amy, you might want to consider doing some weight training...? I think this and walking are the two most fundamental types of exercise, especially for overweight people. And when I say weights, I mean proper stuff - big bar, heavy weights (once technique is mastered), compound movements (squats, deadlifts, cleans etc.). Real movements that will be useful for mobility etc.

That knee injury sounds nasty, though, so take case in anything you do even if it was 10 years ago!

Well, no, there are ways to ameliorate the issues alluded to. But it's not easy.

Still, I suspect it's not something that will cause you a problem

The problem with dieting is this:

Because losing a substantial amount of weight makes the body think it's starving, it learns to cling on to every calorie.

In practical terms, this mean if that maintaining a given body-weight pre-weight-gain requires (say) 2,000 kcal per day, maintaining that same body-weight after you've gained then lost weight will require fewer kcal, say 1,700 per day.

This is a fundamental reason why diets fail. Not only do you have to be in calorie deficit in order to lost weight, you have to maintain a (perceived) calorie deficit in order to keep the weight off.

This is a massively complex area, but here are my thoughts (taken from an essay I'm writing on theories of obesity) -

Excess calorie consumption affects different people in different ways and part of this is down to genetics. A study with identical twins showed that enforced over eating and inactivity led to weight gain (no surprise there) but dramatic variations between sets of twins (but not the twins themselves). The simple thermodynamics of calories in less calories out just doesn't work with a system as complex as the human body.

The Set Point theory is an interesting illustration of the difference 'metabolism' can make, but within rather than between individuals. Basically the theory states that if your body is at a certain weight, it will try and remain there. So if you weigh 65kg your body will try and remain 65kg. Overeat and you might put on a bit of weight, but the result will be that you feel less hungry (probably due to the hormone leptin) and you'll quickly lose that weight.

It works the other way too - it can be hard to lose weight as the body resists the weight loss. If you lose weight, the body goes through hormonal and metabolic changes that persist even once weight loss has plateued. In other words, lose weight and your metabolism slows, making it far easier to put the weight back on. This has been shown to last for at least 6 years and is possibly permanent. So if you put on a significant amount of weight and then lose it, you will have to eat fewer calories to maintain your old 'thin' weight than before the weight gain.

In our evolutionary past, losing a significant amount of weight would have been a likely precursor of death. The body responds to this by flipping into starvation mode, becoming more efficient to make do with the restricted food intake. Muscles become more efficient, converting to type II endurance fibres. After losing weight, muscles burn 20 to 25 percent fewer calories during everyday activity and moderate aerobic exercise. The body is trying to get back up to "normal" weight - its set point. It is a matter of some debate whether the amount of time the body spends at a given weight makes a difference. If you've been overweight for 10 months or 10 years does this affect the above process? Nobody is sure yet.

So if the body doesn't want to change weight, why does it? Well, the change in metabolism and balance of hormones outlined above gives us a clue. Rather than thinking of obesity as simple overeating, perhaps it is better thought of as a malfunctioning metabolism. If all your hormones are working as they should be then the body will resist weight gain. Screw them up, and your natural defences break down. The double whammy is that you gain weight because your metabolism is screwed, and then the process of losing weight screws up your metabolism even more.

Of the various hormones that help to regulate our appetite and body weight, two of the most important are leptin and insulin. Hormones are chemical messengers in the body - a generalised signal that is picked up by relevant cells in the body. However, these cells can become unreceptive to this signal and fail to act as they should. This is generally termed resistance. Leptin resistance interferes with the body's ability to regulate its own weight; insulin resistance interferes with the body's ability to regulate its energy supplies, and can lead to diabetes.