Short answer: yes.
Now for the long answer: I lost 110 lbs in my first year of Paleo (starting it all with a Whole30) without doing any form of exercise at all. And when I say no exercise, I mean I didn’t even go for walks. I only walked where I needed to; not a step further.
But that didn’t last.
On my one year anniversary of starting our Whole30, I found myself 110 lbs lighter, and an idea popped into my head: what if I got healthy enough to be able to get back into the military? Either the Reserve or the National Guard, and then I could finish my 20 years and get some sort of retirement benefits. Besides, I loved serving in the Marines, and I missed the camaraderie and the culture. But, to be able to get back in, I’d have to meet not only height and weight requirements and pass a stringent physical (even more stringent being over 40), but I’d need to be able to pass a physical fitness test which consisted of push ups, sit ups, and a run. So, I began with walking and push ups.
I the beginning, I was only able to do 7 push ups. I was dejected. That was pitiful. But I decided that I would persevere and keep going, making gains naturally and slowly. I never pushed my arms to the point of pain or failure. I would do the push ups only as long as they were easy, and when I felt like I had to start struggling, I would stop. I would then rest my arms for a day, and do them again. I kept at it until 4 months later, I was doing 120 push ups in two minutes.
My walking went the same way. I walked 30 minutes each day until I felt like walking wasn’t doing anything, so I started doing a slow shuffle jog. I would shuffle/jog one day, and then take the next day off. I worked on increasing the distances I could jog each day until one day, I felt that my jogging was too easy, so I extended my pace into a run. I felt like Forrest Gump kicking the leg braces off to run. It felt great! My legs were free, and it actually felt good to extend my legs and to run. On that first run, I was able to go the entire 30 minutes without stopping. That was my first official run. My pace was 11+ minutes per mile, but it was a run.
Fast-forward a year. I just completed my second 5k, I’ve been accepted into and have been serving in the National Guard, and I passed my first APFT in the top 10% of my unit. My average run pace is ~8:30/mile, and I’m working on getting that to sub-8’s hopefully next year.
Did I need to exercise to keep the weight off? No. I kept eating healthy, and that is what kept the weight off. The running and push ups only help keep me fit which is important for my National Guard service, but also allows me to take part in activities I couldn’t dream of just two years ago.
Do you need exercise to lose weight? No. Will adding exercise to your routine benefit you in other ways? Absolutely! I highly recommend doing something. Anything.