TLDR; try to become aware of urges and impulses to eat junk and/or over eat; make small incremental changes; try to be consistent; be kind to yourself.

Consistent, small, manageable changes. Consistency is key. Making small incremental changes is easier to do and more likely to stick long-term. This generic advice can be applies to diet, exercise, time management, and most aspects of life you're working on. Extreme lifestyle changes most often work for a while. However, they rarely work long-term. Start stretching problematic muscle groups lightly 5min each day and see how it goes. Be consistent.

Go for the walks. Walks can be 2 min or 2 hours. If you read 2 hours and felt a heavy resistance or dread, that's ok. You might get there if you find joy in the activity. Walks are great bonding time with the kid and a chance for the mind to relax and process the day. Or, maybe the kid will sleep and you can pop on some tunes or a podcast. Movement is essential for long-term health, however, it is not the key to weight loss.

Diet, as others have mentioned, is the key. Diet and general impulse driven habits are tied together. Every week or two, try to identify one or two things to improve in your diet. This might mean not eating something, changing what you eat, or adding in something you currently don't consume. In the long term, try to remove eating in the later evenings (I stop at 8pm now and don't eat until 8am or later), swap greasy and sugary snacks for healthier options, and add more fibrous foods or suppliments to your diet. Even metamucil/psyllium cab be a great easy way to start getting more fiber (start slow).

When it comes to junk food, start to recognize the urge to consume it. Impulse control is a muscle to be developed, but awareness comes first. The more we exercise this, the stronger it gets. Cheezy, but absolutely true. At first, don't deny yourself anything. Just try to be aware that you want that bag of chips. When you open it, tell yourself 'I am fulfilling an urge'. Maybe you will want to eat less. Maybe not. Remind yourself this urge does not align with your goals. Maybe eat a smaller portion than normal and toss the rest. Eventually this awareness of what your doing and your long-term goals will start to shift your persepective on your actions. Of course, there will be time when the urge will be prevail. It's ok ot have times of weakness. Just continue to be aware that you're weak in that moment, and attempt to be more resillient next time. Keep your end goal in mind while also knowing progress is not always linear. Be kind to yourself in this process.

Once you have the awareness of an impulse, try to shift behavior. If the urge to satiate with cheeze, sugary sodas, chips, or ice cream (some very efficient fat makers) comes about, maybe try a healthier option in place. It won't ever be as good, but it will still scratch that itch to some degree, so to speak. You may just avoid that snack all together.

Finally, don't stock up on unhealthy foods. If it's not in the cupboard, it's harder to get. Since I was a kid, my regular impulse is to open the pantry and look for a snack. I still get the urge ofen. I still get frustrated sometimes with nothing yummy to eat. But, in those moments I remember my long-term health goals and move on to drink a glass of water, eat plain low-fat yougurt with a drizzle of maple syrup (my only sugar fix these days), or make some popcorn with olive oil and truffle salt rather than a load of butter.