While there is no doubt that much of the food available to us is a function of profit-making corporations and government collaboration therewith, the fact is that obesity  - the prime concern here, as salt and fat intake relationships between health are inconclusive, changing month-to-month depending on the latest study - is a function of arithmetic: What you put in is what you get out.

"In most people obesity is caused by eating too much and moving too little. If you consume high amounts of energy from your diet but do not burn off the energy through exercise and physical activity, the surplus energy will be turned into fat." (healthdirect.gov.au)

In the absence of exercise, the average person needs about 2000 calories a day to live.  A Big Mac has 540 calories.  Small fries has 230 calories.  A 12oz can of coke has a 150 calories. So you can have a Big Mac, fries, and a coke for lunch and dinner, and still have an egg and coffee for breakfast and not get fat, WITHOUT exercise.