What if you could eat pizza, cheeseburgers, or fries, and still lose weight? In theory, it can be done. At first sight, weight loss is all about calories in versus calories out. This means you can get leaner on a fast food diet as long as you stay in a calorie deficit. The question is: does it work on long term? What are the drawbacks? Let's find out!

Junk Food: The New Weight Loss Trend?
Ever heard about IIFYM? Or the Twinkie diet? These slimming plans allow dieters to eat just about everything. From chocolate and cake to fried foods, nothing is off limits. However, there's a catch. To lose weight, you must eat fewer calories than you burn.

Let's say your daily target is 1,800 calories. This means you can eat two or three pizza slices, a large serving of fries, a chocolate bar, and other goodies. If you do the math, it fits into your calorie budget. Sounds too good to be true, isn't it?

In 2010, Mark Haub, nutrition professor at Kansas State University, made headlines by losing weight on a junk food diet. He dropped 27 pounds in two months while eating donuts, breakfast cereals, Doritos, Twinkies, and Oreos every three hours. He aimed for 1,800 calories a day, which was less than the recommended calorie intake for his weight.

Surprisingly, his good cholesterol increased and bad cholesterol levels dropped. His triglycerides have decreased by a whopping 39 percent. This shows that calories play a big role in weight loss. However, Haub said that he wasn't feeling healthy and that hewouldn’t recommend this diet to anyone.

Lately, more and more gym goers are embracing the IIFYM trend. This term stands for If It Fits Your Macros. Basically, you can eat anything you want as long as you hit your daily goals for protein, carbs, fats, and calories.

Also known as flexible dieting, IIFYM emerged as one of the most popular yet controversial eating plans. It's not unusual to see fitness models who binge on cookies, lasagna, and pizza without gaining a pound.

Why Junk Food and Good Health Don't Mix
As you see, it's possible to lose weight and keep fit on a junk food diet. Unfortunately, your health will suffer in the long run. The Twinkie diet, flexible dieting, and other similar plans only focus on calories and macros - in the best case scenario - while ignoring food quality.

Let's take chocolate cookies, for instance. They contain nothing but sugar and empty calories.

When foods are heavily processed, they lack nutritional value. Their protein content is close to zero. On top of that, they’re packed with simple carbs that cause blood sugar spikes followed by crashes. This increases your risk of diabetes, metabolic syndrome, insulin resistance, and heart disease.

Processed foods often lack fiber, which is crucial for digestion. This nutrient keeps blood sugar levels stable and prevents insulin spikes. Moreover, it suppresses appetite and increases satiety. Just think about how full you feel after eating an apple, oatmeal, or salad. Can you say the same about potato chips? Not really.
Nutritionists recommend whole, natural foods for a reason. Fresh fruits, veggies, nuts, seeds, fish, and grains support optimal health and well-being. Calories do matter, but they are not everything. Food quality is way more important.

Summary

• In theory, it is possible to lose weight on a junk food diet. As long as you’re in a calorie deficit, the pounds will melt away. 
• Popular diet plans, such as IIFYM, support these claims. 
• Unfortunately, junk food and good health don’t mix. Even though you can get leaner while eating fast food, the long-term effects shouldn’t be overlooked. 
• Food quality and nutritional value are more important than calories.