The grocery list can only be as simple as your meal plan, but with a few minutes each week spent tweaking your plan it's possible to get plans that work for you.
First and foremost, the biggest change you can make is set the Generator Focus to "Groceries" in the Settings menu, and the planner will optimize for the lowest waste.
Other than that, here are some tips:
Reduce Meal Variety - The stricter your diet, the less variation will be possible due to the amount of foods that don't fit your macros. The best places to start are with:
Make substitutions between similar foods. If the grocery list tells you to buy spinach leaves and lettuce, you can use one of them for both recipes without changing the nutrition very much. You can make the substitution on your own, or personalize the recipe to make sure the difference is recorded and the new recipe is used in the future.
For the purposes of general health, you can pretty much eat as many non-starchy vegetables as you want without affecting your plan, and more vegetables are generally a good thing. Feel free to add in leftover vegetables to any of your recipes if they are in danger of going bad.
If you see multiple things in your grocery list that could be easily substituted for one another, don't hesitate to make substitutions. You can either make these substitutions mentally while you're grocery shopping, or combine the amounts directly in your grocery list. This is a little inconvenient, but we don't currently have the ability to allow you to set preferences like always replacing whole milk with 2% or anything like that.