Weight loss & TTC

ok. so I'm very overweight. 5'8 260. At my best I was 172lbs and a size 8/10. Ideally that's my goal. I really want to get back into eating well and exercising, but we're TTC, first time. Will it adversely affect our chances if I begin to diet and exercise again? I don't ever remember missed periods from diet and exercise before, but a coworker told me it would cause issues. It wouldn't be a crazy diet, just sticking to a calories goal and moving more. I have a desk job.