What Age Do Skinny Guys Gain Weight?

When it comes to gaining weight, skinny guys always tend to struggle. No matter how much they eat, they can’t seem to gain a single pound and that’s usually due to their fast metabolism that’s constantly burning calories. I personally struggled with this during my entire teenage days and people would often tell me: Don’t worry, you’ll gain weight as you age! Just wait till you grow old a little bit and you’ll naturally gain weight! With that being said, will skinny guys really gain weight as they age? At what age does that happen?

Skinny guys will generally start to naturally gain weight around the age of 17 and 18, but this time can be significantly decreased with training and the right diet. 

In this article, we’ll talk about if skinny guys really gain weight as they age, the age range in which this happens, and how you can significantly decrease it. 

Do Skinny Guys Really Gain Weight as They Age?

In order to answer this question, let me tell you a story about myself first. During my teenage years, I was extremely skinny and I’m not even exaggerating. I was 15, 5 foot 9 tall, and weighed about 100 pounds. According to a BMI calculator, I was considered severely underweight which showed, especially when I took off my shirt.

People would often come to me and tell me that I would naturally gain weight as I get older but I didn’t believe them at that time and thought that it was only a myth. I honestly thought that I was gonna stay like this my entire life but little did I know, I was so wrong. 

Fast-forward a little bit and right when I became 17 years old, I started noticing some change in terms of my weight. Surprisingly, I started to naturally gain weight due to the fact that I was feeling hungry way too often and was constantly eating. It wasn’t much but at least it was some decent natural progress that I was proud of.

Fast-forward again to the age of 18, I was 6 feet tall, and I managed to naturally gain 30 pounds and that’s when I decided to join the gym to kick-start my 3-year fitness transformation journey. Little did I know that that would be the best decision of my life as you can tell from the picture below.

eliass 3-year fitness transformation journey

In other words, skinny guys will naturally gain weight as they age due to different factors such as puberty, the fact that you start getting hungry more often, and the metabolism starts to slow down.

We’ll talk more in-depth about these factors in the next section.

At What Age Do Skinny Guys Gain Weight?

at what age do skinny guys gain weight

As I mentioned in the beginning and according to my own personal experience, skinny guys will generally start to naturally gain weight around the age of 17 and 18 and that’s due to different factors:


Around the age range of 17 and 18, most guys will be going through the final changes of puberty. That’s when the testosterone starts to kick in which results in a natural growth in terms of bone density and muscle power. 

Around this age, guys will become stronger and grow in size which will lead to an increase in weight and there are also some that will start developing fat.

Increased Appetite

Around the age range of 16 to 18, the appetite will naturally start to increase especially for guys. This was also the case for me, I was constantly getting hungry and feeling the urge of eating something. In most cases, it was just my mind talking since my body wasn’t in need of any more energy but during this time, you need to take advantage of this factor and eat whenever you feel like it in order to maximize your weight gain. Just make sure you’re not overeating otherwise you’ll become overweight (which is not what you want).

Decreased Metabolism

The more you age, the more your metabolism starts to slow down. And metabolism is one of the main factors that control weight. It’s the amount of energy needed for your body to maintain itself. During your teenage years, your body will constantly need energy which is why most teenagers are skinny. As soon as you hit your 20s, the metabolism starts to slow down by 10 percent for every decade after this time.

How Can Skinny Guys Speed Up the Rate of Weight Gain?

If you can’t wait till you’re 17 or 18 to gain weight, there are some things that you can do in order to speed up this process and start gaining weight and building muscles during your teenage days (While benefiting from the factors that I mentioned earlier like puberty)

Practice a Sport

Practicing a sport is one of the best ways to gain weight and build a solid foundation for your muscles, especially if it’s a sport that demands a lot of physical effort. I’m talking about martial arts, basketball, tennis, and anything that engages your muscles. After every session, you’ll be returning home longing for something to eat and your muscles will be sore from all the work that you put them through. You’ll learn a lot of useful skills, meet new people along the way, build up your confidence, boost your self-esteem, and most importantly, gain a lot of weight. 

Start Weight-Lifting

In my opinion and talking from pure experience, this is the best way to speed up the process of gaining weight and building muscles. As you can tell from my 3-year fitness transformation journey, joining the gym was the best decision of my life. It’s going to get you addicted to a healthy lifestyle early in your life. You’ll develop a lot of good habits that will benefit you throughout your entire life. It’s going to be challenging, especially if you start young, but it’s one of the most rewarding paths that you can take, just learn from my story!

Start Eating a Lot

If you want to really speed up the process of gaining weight, there is no other way around it, you just have to eat more. If you’re young, always keep in mind that your body is constantly burning energy throughout the activities that you do during the day, that’s why you always need to reach a calorie surplus (meaning eating more than what your body is burning so the excess can be stored fat or go directly to your muscles).

Whatever the amount that you’re eating now, be sure that it’s not enough (since you’re skinny and not gaining any weight). Add an extra 500 calories to your diet for a month and see the results of that, if you’re still not gaining any weight, add another extra 500 calories and see how that goes, eat more protein, more fat, and so on. You’re still young and you still have all the time in the world to experiment with what you’re eating so take advantage of it. 


As you can see, most guys will start to gain weight around the age of 17 and 18 due to puberty, an increase in appetite, and a slow down of the metabolism. However, you can significantly increase this time by practicing some sport, starting weight-lifting, and eating a lot.

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