Practically speaking, arthritis can make it more challenging to exercise regularly due to increased joint pain, discomfort, and stiffness. Since exercise is an integral part of weight loss and weight management, arthritis can make it difficult to lose weight in that way. With that being said, arthritis should not directly cause weight gain. Since regular exercise can be difficult with arthritis, you may find aquatic therapy and exercise beneficial, as warm water is known to soothe and relieve pain and stiffness from arthritis. Low-impact exercises may also be helpful.