Interesting that physical attractiveness can be an emotiinal need. I might rather say sexual attractiveness, which is more encompassing. I won't get into it, but we are ok there.
This is actually a very great update and gives you a much stronger platform to effectively address your original question.
You are here because she is not filling an emotional need you have, which is causing your relationship to suffer. Recreational companionship and domestic support are two other types of typical emotional needs.
For a temporary season, let's say three months, ignore the unkind tones of her requests (or even demands) and do your best to address the content of the complaint while also prioritizing and pursuing 15 hours per week of undivided attention with each other (without kids and pets; outside of the home on 3+ hour "dates" is best).
During these three months, praise her attractiveness particularly during times you are making love, but also specifically other times, too. You want to build up an unshakably solid confidence in her that you do find her attractive in her current condition. Women can tend to doubt their bodies and attractiveness all day every day, but you want her to have a certain knowledge that you have no doubts.
Once you have purposefully solidified her certainty of your attraction to her, then you can approach her about your desire to be able to share your recreational pursuits with her and your strong desire for her ambulation to improve so you can keep doing things together.
You can affirm that you are attracted to her the way she is - as is evidenced by your sexual performance since men have a hard time performing if there is no attraction - and this has NOTHING to do whatsoever with her appearance. You can assure her that you find her sexy and attractive.
You can also mention that it has come to bother you that she is unable to participate in parenting the children along with you due to her limited abilities to walk. In this, focus on recreational things you do with the children together as a family rather than she can't help with the children you while you cook. Don't get her thoughts distracted into "he is demanding more help" because that will take you on an unproductive goat trail.
If 20 pounds would make a difference in her ability to walk, just focus on 20 pounds at that time (after the three months) - don't wrap the whole 150 pounds into this request as that would be enormously discouraging to her, may feel impossible and would cause her to doubt your sincerity about her attractiveness. Ask her how she would feel about losing 20 pounds to see if that helps her ability to walk. After the 20 pounds is lost, if she cannot walk much better, the two of you can consider another 20 pounds, etc. Take it in small chunks that feel more achievable.
If I were a homeopathic professional, I would consider having her start with a detox cleanse for 7 days. You could actually do this together. Maybe the professional would have her start with a 3 day detox if a 7 day period seems unachievable.
What this also does is demonstrate that to a person's self is that you can control your appetite and what it feels like to do so. It allows you to know what it feels like to say no to the cheat meal - and that it will be ok. Often someone in her situation will lose 10 - 15 pounds during a detox week so it will give her an enormous boost towards her goal. It also weans off the cravings that serve to so effectively defeat weight loss attempts. After the detox it is much easier to say yes to healthy eating and no to foods that are no longer so strongly craved.
If necessary, the homeopathic doctor could have her visit every day to gauge how she is doing during this detox so she has a lot of support (aka accountability) to make it through to the end.
Or, if in your judgement she'd be willing to do this with you without a professional, it certainly is likely to be safe for the two of you to do it on your own. My concern with this is that it puts YOU in an accountability role moreso than a third party, and that is a role
you do
not want to assume.
A homeopathic professional may have more or better ideas than starting with a detox - that's just from my personal experience. I find it to be a great start to realizing that an appetite CAN be controlled if you choose to do so, as well as a great head start towards eliminating cravings in support of weight loss goals.
A detox can be repeated periodically, particularly when the cravings start erupting again which are serving to defeat weight loss goals.