I've been very health-conscious over the past few years - I've never been overweight, but I've always been motivated to have a fit-looking body and a flat stomach, so I've been very disciplined when it comes to diet and exercise. I generally stick to a very low-fat, low-carb diet, and exercise regularly.

However, lately, people have been telling me I look very underweight. I recently checked my BMI, which came to 17.9 - so, I'm officially underweight.

So obviously I need to gain weight. But generally, whenever I gain weight I gain it in unsightly places, like in the abdominal area. Is there any way to increase my BMI without adding fat to the abdominal region?

1 Answer 1


The first thing I would recommend is not using BMI to determine whether you are over or under weight. Instead go by body fat composition.

That said, in order to gain weight, and not be fat you'll need to do a couple things:

  • Eat some fat and carbs. I'm not telling you to go nuts, but this is going to help get more weight on. (more on the later)
  • Build muscle. I'm not saying be a body builder, but you want to increase your lean mass to keep your body fat low as you gain weight.

If you are a guy, 10% body fat will give you a six pack and 15% will be a fit look. If you are a woman, it will be higher (something like 23-28%)

Since you are on a very low fat, low carb diet, your body probably doesn't know what to do with that type of food. Be careful with re-introducing them. There's a couple strategies to do it:

  • In the AM meal, incorporate grain carbs, fruit carbs, dairy fat/carbs along with your protein. I don't have my guidelines handy, but one serving each at the most. Do this for two weeks. After that, you can have some carbs with your dinner and fats with your lunch.
  • or you can add one serving of one type of carb each day. Introduce a new one each week until you have all the sources covered.

Lastly, I shouldn't have to tell you this, but you still want a good amount of protein. At least 1g of protein per pound of lean body mass while you want to gain muscle. Of course with the extra protein, drink lots of water.

Finally, the exercise you choose is up to you, but you won't build bigger muscles (getting heavier while not getting fat) without demanding more of them. Some options are:

  • strength training (obvious one here)
  • swiming (excellent full body workout and cardio all in one)
  • running
  • climbing

The idea here is to demand more of your muscles so you can build them up, and feed them protein so they can increase.

  • 1
    I was going to respond to this question, but you didn't leave anything out that I could add to the discussion :) +1
    – Aardvark
    May 26, 2011 at 14:29
  • What kind of running do you suggest? Distance runners, as a general rule, are also underweight (I'm one of the bulkiest guys in my circle at 6' and 140 lbs, a BMI of 19 - don't have a recent body fat percentage measurement) May 26, 2011 at 19:45
  • @Berin-good answer! I've recently gained some muscle mass since being underweight. I am a competitive swimmer so this lean muscle mass has been beneficial for my training. But I've also gained a bit of cellulite on my legs - does this mean that I've gained too much fat in the process of gaining lean muscle mass?!?! My clothes all still fit and I am definitely musclier, so where has this cellulite come from? Any help would be very appreciated!
    – Bee
    Jul 13, 2012 at 12:10
  • Think of it this way. If you are 100lbs with 20% body fat, and then you increase your weight to 120lbs while maintaining that same body fat, you will have more absolute fat. At the start, that would be 80lbs lean mass and 20lbs fat. At the end it would be 96lbs lean mass and 24lbs fat. The cellulite is unfortunately, where your body wants to deposit its fat. That is genetically controlled. Jul 13, 2012 at 12:33

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