. . . Sit-ups are anaerobic exercises, and anaerobic exercises are muscle training. If you do a lot of anaerobic exercise plus a lot of calories and protein, you will definitely grow muscles, your waist will definitely thicken, and your abdominal muscles will definitely become bigger. But the common misconception is that muscle is not equal to line, and line is actually equal to body fat rate. A fat man with a huge appetite, a 120 kg manual worker all the year round, has a beautiful figure in the gym. In fact, fat people have big abdominal muscles and strong strength. It is wrong to say that sit-ups can lose weight. Actually, sit-ups can reduce fat. Any muscle gain behavior, as long as it can control the diet and reduce the intake of fat and carbohydrates, is fat reduction, but fat reduction is not weight loss, because increasing muscle mass will increase the basal metabolic rate. It is possible that you will lose weight and gain weight, but your figure will look good. So if you just do sit-ups, control your diet, and don't do a lot of aerobic exercise, you can gain muscle. But what I'm saying is that muscle gain is not to increase waist circumference, but it's the same reason. Muscle gain is not fattening and thickening, and fat loss is not simply weight loss. If you just want to thicken your waist, it's easy to do. Practice sit-ups and then overeat a lot of high-calorie and high-sugar foods, so that the muscles and fat on your waist increase the fastest, and the fat volume of the same quality is much larger than that of muscles. If you want to have a good figure, you can only do it step by step, and try to avoid getting fat. Then you need to control your diet, increase your total appetite, eat more protein, eat less oil and sugar, and do some aerobic exercise. This is a difficult and gradual process, and it is definitely not as fast as gaining weight directly.