Half the meat, all of the flavour. Red lentils melt into the sauce and thicken it, so nobody notices them, and they let you use less beef without a thinner sauce. The secret is time: the onion, carrot and celery need ten minutes, and the sauce needs at least half an hour.

A serving has about 43g of protein and 13g of fibre. A typical bolognese with white pasta has about half this fibre. The difference comes from the lentils, the wholewheat pasta and the vegetables in the sauce.
Less red meat, without missing it. The NHS advises people who eat more than 90g of red or processed meat a day to cut down to 70g. Here 400g of raw beef serves four, about 70g cooked each. The lentils make up the bulk the extra meat would normally provide.
Beef is one of the best sources of iron and zinc. The iron in meat, called haem iron, is absorbed much better than the iron in plants, and it also helps you absorb the iron from the lentils. Zinc contributes to the maintenance of normal testosterone levels, and red meat is one of its main sources: see the best diet for testosterone. For women with heavy periods, see iron deficiency and heavy periods.
The portion of pasta is 75g dried per person. That is a normal portion, and the fibre in wholewheat pasta slows down how quickly its carbohydrate is digested. That is why it is tagged for blood sugar. If you train hard, you may want more; if you do not, you can use 60g.
Use gluten-free pasta and check the stock if you need it to be gluten-free. For another beef dinner with beans, try the beef and black bean chilli.