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 to set the Generator Focus to "Groceries" in the Generator Settings, and the planner will optimize for the lowest waste.
Open the left sidebar menu and select Generator under Plan Settings. Set the "Generator focus" setting to Groceries. This comes at the expense of variety and macro accuracy, so you'll have to decide if the trade-off is worthwhile.
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:
Adjust Meal Settings - The number one thing you can do to reduce the size of your grocery list is set your "Meal complexity" setting to "simple". To adjust the meal settings, open the left sidebar menu and select Meals under Plan Settings. You can select the title of any meal to open the settings.
Leftovers - By including leftovers you basically get 2 meals for the price of one as far as groceries are concerned (or however many meals you select for leftovers). On top of that, you save on prep time. See more using leftovers here: How do I automate leftovers or meal prep?
Recurring Foods - Setting up lists for each meal makes the plans more like something a nutritionist might give you, with a selection of foods that fit your needs and form the basis of your whole plan. This is especially important for Keto diets and people with food allergies since they are already picking from a limited number of recipes. See more about Recurring Foods here: Using Recurring Foods to incorporate more of your preferred foods
Include Restaurant and Prepackaged Foods - To avoid recommending any foods that are not available in your area, the generator does not utilize all of our databases when generating plans. Adding branded foods and restaurant foods will do a lot to shorten the amount of ingredients you will need.
Make substitutions between similar foods
If the grocery list tells you to buy spinach and kale, 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.