Do keep in mind that everything written below is my opinion, through my experiences, I am no professional in terms of health or fitness. But I'm always ready to share any suggestions, if necessary.
Weight gain has been a common subject between women, different parts of the world have different expectations about how a girl should look like.
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It is no news that every other girl these days succumbs under the social pressure of looking a certain way. One kg down and the society tells her she "too thin". One up and she's puts herself under the pressure of being fat shamed. Every girl I've known has her own way to control her weight diets/ gyms/ skipping meals/fasting/drinking green tea you name it! They don't consider whether it works or not is secondary. But remember when you starve yourself for 5 days you only lose 5 days, especially when the diet is only for temporary results. So please eat what makes you happy, a good home cooked meal like your mom would make for you. Do remember that once you deprive yourself from carbs and other vital nutrients you crave twice the same once you get a chance.
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The best way to control weight gain is to increase your daily activities, just climb those stairs, use the washroom on a different floor at work, drink a lot of water, and walk as much as possible. A few small changes in your lifestyle can give you permanent results. Timing is also very crucial. If you're having your meals and sleeping at the correct time, it reduces the risk of weight gain. You're supposed to eat when the gastric juices are produced in your stomach. Before enrolling in any fitness program these are a few simple rules to apply in life. I have achieved my results by first applying these changes in my life, I have lost over 10 kilos over the past 1.5 years, and a total of over 20 in the last few years of my life.
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You need to first accept who you are, and be happy about it. Value everything your life has given you, don't take it for granted. Once that is done you would easily understand whether fitness is your priority. Set realistic expectations from yourself. But do keep in mind that 0 is not a size, a curve is also a shape, small tummies look cute and confidence is the new sexy.