Well - a 6'2", 140-lb, 22 years old male has a basal metabolic rate of 1728 cals/day. So - with a diet of 1800-2300 cals/day and with aerobic exercise (bike riding) ... you're not going to gain any weight.
If you want to gain weight ... you need to increase your caloric intake (to 3000-3500 cals/day) and do some weight/strength training. You can increase you calories with complex carbs, proteins, legumnes and fruits.
Since you are in school - you have a couple of free resources - one is the physical education department, the other is a nutritionist that oversees the food service on the campus.
Now, as to the "weight" requirement ... it appears the RCMP did away with that back in the 70's - replaced that with the Physical Abilities Requirement Evaluation (PARE). But, if you just want to be a cyber crimes geek - you can get on in the Integrated Technological Crime Unit (ITCU) as a civilian employee of the RCMP.
You might search the RCMP website
to get more information - and information on how to contact them for more up-to-date information.