Here is some great news for plus sized people. There are several models of heavy duty tricycles that may be just right for you. The lions share of adult tricycles have weight limits of up to about 250 lbs so you may have assumed that there was nothing available for you. However there are tricycles that can handle up to 600 lbs! Few riders need anything this rugged but certainly up to 350 lbs is not unusual.
Actually heavy duty tricycles are usually found in industrial plants but they aren't all that different from a more conventional tricycle. Where they do differ considerably is in the size and the ruggedness of the components.The wheels are generally larger and the components are more rugged including the frame, chain, sprockets, and bearings. Just as the name implies they are designed to handle heavier loads and more severe duty.
Most heavy duty trikes come with a front V brake with heavier brake pads and a rear coaster brake like the bike that you rode as a kid. A quarter turn backwards on the pedal will stop the rear wheels. Riders with arthritic hands welcome this feature.
Unlike a bicycle, a tricycle rider can ride as slow as they want without any balance problems and can stop and rest with both feet on the ground.These are definite benefits to plus sized riders.
Husky and Trailmate are some very popular manufacturers