Of course, most of the world lives on far less food than that, and the nutritionist readily conceded that the typical diet in China is healthy and could easily be accommodated in $21/week. But for Americans, it is impossible. Bah!
So I normally spend far more than that for food (mostly due to luxuries like rare tuna steaks and fresh herbs, and eating out for lunch, and dinners), but honestly, I could do quite well on $42 a week (for two people), and still cook and eat the same things.
Shopping list: (from local safeway)
(plus room for $18 worth of a 20 week supply of corn/sesame oil, vinegar and salt and pepper, and soy sauce and assorted spices/condiments)
One dozen large eggs. $1.79
One gallon milk. $2.75
Safeway Large 32 Oz yogurt. $2.50
12 bananas. $3.00
18 oz Kellogg Corn Flakes (18 servings) $2.00
4 lbs. Green Cabbage. $2.
1 lb. Celery. $1.99
2.5 lbs onions. $1.99
2 lbs carrots. $1.89
1 lbs broccoli $1.50
5 lbs potatoes. $3.29
14 oz skippy peanut butter (12 servings) $1.50
1 loaf 24 oz safeway 12 grain bread $1.69
2 lbs botan calrose rice (20 servings) $2.00
1 lbs barilla pasta (8 servings) $1.00
1 lbs dehydrated black beans (12 servings) $1.19
1.5 lbs perdue boneless/skinless chicken thigh (8 servings) $2.99
1 lb lean ground beef (5 servings). $2.99
8 oz Safeway Cheddar (8 servings) $1.50
2 bulbs garlic. $0.44
It wasn't even hard. My first attempt came in well under. These are all meals that I would normally eat, and with plenty of left overs. Probably would gain weight if I ate everything there. And if I were to adjust probably could cut some carbs in favor of vegetables and more meat. But enough to have (stir-fried) chicken 2 nights. Mexican with refried beans and cheese and sauteed onions and rice and yogurt (yogurt makes a healthy replacement for sour cream). Cheese burgers (1/4 pounders) one night with baked fries and sauteed onions. Beef/Potato Hash another night. Bean/pasta salad for one nights. Baked potatoes with beans and cheese and yogurt on another night. Breakfast is at least maybe 2 eggs each and hash browns, for 3 mornings. With enough cereal, yogurt, bananas, milk on other mornings, to be stuffed. Enough for at least 12 peanut butter and banana sandwiches (could mix it up with grilled cheese) plenty of carrot sticks and celery (with peanut butter). Probably could do a bit more veggies, but I think what I have is not far off from the fairly vegetable heavy diet I normally east. With ~10 lbs of vegetables, that's roughly 60 servings. Could make cabbage cole slaws (using yogurt and vinegar and sesame oil). Diced celery with sesame oil and vinegar is quite good. If I had to rebalance, maybe fewer carbs, more veggies. I count roughly 90 servings of carbs. That's 2 people over 7 days, still about 6 per day.