More and more people are trying to change their 'lifestyle' (tutaj wg mnie ma byc l. mnoga bo mowisz o 'people'). One of the most important 'thing' (one of...thingS) is food, which 'we' (dlaczego akurat 'we' jak wczesniej mowislas o nieznajomych 'people') should choose very carefully. People have little time, so they prefer TO buy something at (tu brakuje przedimka) shop, than prepare (brak przedimka) meal by 'yourself' (calkowicie zle, tutaj mowisz o 'people'-l. mnoga).
The main advantage (tu brak slowa) this choice is that 'we' (zmien) can buy everything, 'what' (to jest kalka z polskiego 'co' ale jest zle, pomysl co w jez. ang tutaj dajemy) we really need. It is very easy, additionally at (brak przedimka) shops (brak slowa) 'is'(ale tutaj odnosz sie do 'products-to jest l. mn to czasownik tez musi miec l. mn) many produtcs in one place. It's comfortable for people, who work overtime, but very often we haven't got (brak przedimka) idea (tu brak 3 slowa) 'to' (zle slowo, tutaj FOR) lunch so we choose something prepared by other people.
Secondly, it's cheaper than 'buy' BUYING ingredients, which are on (brak przedimka) shopping list.
It's 'junky' (nie, napisz 'junk' co znaczy junk) and fatty food, which can 'leads' (dlaczego dalas tu 3os.l.poj, wystarczy LEAD) to food poisoning or we can put on weight.
Eating prepared food 'have' (zle slowo, tutaj HAS - food-has) good and bad sides, but we have to keep (brak przedimka) balance between (tu brak 2 slowa) 'fitnes' (blad ortog) fanatic and (brak przedimka) obese person.
Zrob cos z tymi przedimkami (a, an, the) - bo z tym to masz jeszcze problemy.