Romelu Lukaku is badly out of form and Manchester United fans know it.

The disappointing 0-0 draw with Crystal Palace marked another game without a goal for the Belgian striker, who is experiencing his toughest spell since arriving at Old Trafford last summer. 

There can be little doubt that he enjoyed an impressive debut campaign - with 27 goals in 51 outings - but that form hasn't translated to success this season. 

Lukaku has failed to score since September 15, which is a total of 11 games in all competitions and Jose Mourinho took the decision to drop him for four consecutive games.

The likes of Jesse Lingard, Anthony Martial and Marcus Rashford have been preferred in the frontline with Lukaku looking sluggish and failing to score.

Lukaku's recent struggles

It's a poor run of form that has confused Mourinho himself, who revealed that he attended Belgium's recent game with Switzerland to get a better understanding of his struggles.

"Roberto invited me to meet him which I decided not to because I don't like to disturb people before matches," Mourinho explained. "But I was with Roberto on the phone trying to understand the problem and evolution of the problem."

It's a confusing situation and one that has United fans hypothesising on the cause of Lukaku's goal drought, with one theory concerning his physique.

Reddit post on Lukaku's physique

After the 1-0 defeat to Juventus last month, supporters started to question whether Lukaku had put on too much weight in muscle and whether that was effecting his dynamism on the pitch.

At first, it sounded a little debatable but the difference in Lukaku's body over the last year is remarkable.

And after another disappointing result at the weekend, a post has appeared on the United Reddit page that underlines the worrying change in Lukaku's physique.

The post shows a recent photograph of Lukaku alongside of an image of him celebrating against Swansea City in August 2017. The difference is clear for everyone to see.

Check out the image below:

The fact the image has been 'up-voted' over 300 times shows supporters feel pretty strong about the theory.

Bulking up is unlikely to be the sole cause of his recent stagnation, but the extra muscle looks to have effected his movement and pace.

Physical conditioning is becoming increasingly important in top level football and the United team might have to look at Lukaku's preparation going forward.

That being said, the exact facts and figures remain unknown and only those at Carrington will truly know how the Belgian has switched things up.

All isn't right when it comes to Lukaku this season and you can't blame fans for turning to a reason that seems to be gathering more and more evidence

Do you think Lukaku's conditioning is effecting his game? Have your say in the comments section below.