What is it?
Also known as weight cycling, yo-yo dieting is a continuous pattern of loosing and gaining. It encourages taking up fad diets, like the low carb-high protein and starving being the most common ones. Weight loss with the help of this method can range from two to five kilos per cycle; sometimes it can even go up to 25 kgs!

The cycle
Step 1: People go on a crash diet that increases the metabolic rate and leads to instant weight loss.
Step 2 : Weight loss leads to quitting the diet plan and returning to the normal eating habits. Now you eat all the forbidden foods that have so recently helped you shed the weight. This lowers the metabolic rate.
Step 3: So you instantly put on weight and in frustration, go back on the crash diet. You lose weight immediately, but the pattern is set.
SOURCE OF THE ARTICLE – TIMES OF INDIA
Disadvantages
Leads to weight gain
The body adapts to the chronic dieting pattern by lowering the metabolic rate to cope with the energy deficit during the starvation period. So if you need 1850 kcals to go through a no dieting day, on a low calorie diet, your body drops down your metabolic rate. When you return to your regular eating pattern, your body doesn’t require the calories you were taking earlier. The excess calories result in weight gain.