A calorie is a calorie.

It's a unit of measurement.

Just like a mile is a mile.

It's a unit of measurement.

But.

Some miles are highways.

They're flat, well maintained and take you directly to your goal.  You can drive a mile on a highway in 4 minutes and they're safe.

Some miles are uphill in a mountain. 

They're full of barely contained rocks that slip as soon as you put your foot on it.  They're dangerous and they'll take you 2 hours to complete the mile. And you also might die.

They're both a mile but they're not equal.

Calories are the same. And the calories you choose can make your diet feel like it’s going smooth and directly towards your goal, or they can make your journey feel like it’s up a dangerous mountainside hill.