Why does it take me a week of diet and exercise to lose a pound but when I have a few "cheat" meals in a weekend a gain back 2.5 pounds?

First of all, you can gain a lot of "weight" without gaining any fat, for instance by how much water your body is currently holding on to or how much muscle you've built in that given time. Secondly, 2.5 lbs is a lot to gain in 2 days, assuming it was all fat—a few "cheat" meals doesn't explain that many calories. Thirdly, watching what you eat is far more effective for loosing weight than exercise is. I'm not advocating for cutting out exercise, but when it comes to weight loss I'd definitely put the emphasis on what you're putting in your mouth over how many hours you spend in a gym. For instance, I'm 170 lbs, 32 years of age, and 6'1". After 1hr jogging on the treadmill I'm told I've burned 500 calories. About 75 calories of that 500 is the calories being burned by merely being alive, i.e. if I was just standing there I'd burn those calories in that hour. So only about 425 calories can be ascribed to my actually running. 1 medium soft-serve ice-cream in a plain cone is about that many calories. What would you prefer: avoid eating one, or run for an hour? Of course, this is too simple. Exercise and food have all sorts of interesting effects on you physiology and brain chemistry so looking at weight loss from a purely caloric angle can be misleading. Still, it has some value so I'd consider this next time your swallowing beers and eating snacks.

I believe this is just a temporary weight gain consisting of calorie surplus and water retention. Your cheat meals might be high in sodium therefore you will retain more water. Generally, I can fluctuate 10 lbs throughout the day depending what I eat. I find cheat meals to be beneficial to my overall fat loss progress even though I will feel fat for the following day or two of my cheat days.

sometimes at the beginning, you just lose some water in you body rather than fat after diet and exercise, so you would see your weight changed but weight regain would  happen if you not keep going to control diet and exercise. loss weight is slow process, requiring patience. running is an extremely efficient way to burn calories and drop pounds. If you could running every day around 40~60minutes and stay away from chips and chesses and chocolate, you would see your weight change after one month, and then keep exercise as your routine work, you don't need to worry about weight regain after having  once or twice time "cheat" meals

Scale is no good measure, fluctuations in the short time period are due to water retention. You should measure your waist and hips, and try to do it once in 2 or 3 weeks. Forget about the scale.

[Edit: Initially I assumed that the weight gain was caused by what is described in my suggestion to weight loss below. However commented on it being wrong and I further dwelt on this question and looked for a little more information and now my views are that it's quite improbable for a 2.5 pounds weight gain by fat within a weekend. Likely it's due to water and some of the symptoms are general feeling of puffy hands or feet. And the possible causes are high sodium (processed food) and carbo intake. A way to determine whether the weight gain is due to fat is if you do a fat monitor before & after the weight gain. Thanks to Tom for pointing out my mistake. But I still hold my views on what is described below.] Going on a diet to lose weight is one possible way but it's probably better to eat healthily in the long run and build some ways to ensure calorie intake < calorie expenditure. How to lose weight by skipping meals the proper way. Disclaimer: Before you try this method, please ensure that you do not have any pre-existing medical conditions and are in good health in general. Also, it will not be a sudden & immediate but be a very gradual one. It's a good idea to consult your friendly family doctor to ensure you are able to do this weight loss method safely. The idea is to consume overall less calories than you expend and yet trick your body into not storing food as fat. Try this regime as a weekly cycle. Eat every meal as usual to the point of 80% fullness. Try your best to ensure the timing of your meals are fixed to get your body into a rhythm. In between, if you feel hungry, eat healthy snacks like fruits or nuts (non delicious ones to discourage over-eating) and just enough to ensure your stomach is not hungry. When you do this, your body will not store food as fat. To understand this, it's related to our origins when we were hunters/ cavemen where food was scarce and not in constant supply. Then, whenever we managed to find food and have a good meal, the body will store a portion of the food as fat in order to be able to survive till the next who knows when meal. And what is the cue for the body to do this? It's the feeling of hunger just before you eat your meal. Simple logic isn't it? And when you are hungry, your body will not burn fat, instead it burns your muscle to conserve your body fat until the next meal. So back to the plan, after doing it (fixed eating @ 80% fullness) for a week, you will have gotten your body into a nice rhythm of expecting and getting food on time & on target. This will prevent your body from storing food as fat. Then in the 2nd week onwards, every two days of a week, say Tuesday & Friday, skip lunch and have some light snack (fruits & nuts) to prevent your stomach from being hungry. So this way, you will expense more calories than you consume and more importantly, your body feeling that food is constantly in supply, will burn your fat instead of your muscle mass. So having understood the proper way, let's see what others are doing it wrongly. Some people will eat a heavy breakfast, skip lunch and eat a heavy dinner almost all days of the week. This is the worst strategy because you likely do not cut down on your total intake calories (heavy breakfast & dinner) and yet your body feels hungry everyday. This means at every meal, your body (caveman thinking) will convert food into fat and expend your muscle mass while storing the fat till the next meal! Try it and leave me comments on whether it's successful or not! Good luck. Some further reading: http://www.nerdfitness.com/blog/2013/08/06/a-beginners-guide-to-intermittent-fasting/

You probably won't like the real answer :)  What is happening is that your cells normally store some glucose and their stores of glucose can be depleted by diet.  The low glucose causes a lot of water weight loss.   Also if your diet is low sodium, it will also contribute to water loss. When you eat normally you just restore the glucose and sodium levels and the cells rehydrate.  so the glucose isn't a 'real' weight loss.  The salt can lead to a bit of excess water retention also. If you want to track weight loss, use a plastic/cloth tape measure  and check your waist measurements (measure both gut sucked in and exteneded to maximum).  Do that about once a week and it will give you your real weight loss.

Those 2.5 pounds are mostly water weight. You need 3500 calorie in excess to gain one pound of fat and for 2.5 pounds you will need to eat 8750 calories in excess. It is very impossible. Cheat meals are supposed to help you have a mental break from dieting but if you are going to start to get upset from temporary water weight gain the day after or a few day after then cheat days or meals may not be the best for you. You can learn more in detail by checking out my video on this here: Hopefully this helps :-)

Yes, it makes total sense. You cant have cheat weekends. You can only afford cheat meals. One cheat meal per fortnight is the maximum you can go down to. And your body is of the Endomorphic types. Endomorphs tend to gain weight easily than lose weight. Ideally you should lose abt 2 pounds per week.