When you put money into a fast food chain they are able to grow and expand, sharing there food with more people. When the food is low quality and oily this leads to heath problems such as obesity. I'm sure obesity is not something anyone wants to support. On the other hand if you invest in a restaurant that will take you're investment and share there nutrient dense food with more people. You are then supporting peoples health instead of illness.
A restaurant could have a very thin menu and be better than a restaurant with tons of menu items. Quantity does not mean the quality is better, or the patronage. Even a hotdog cart could do better than a restaurant with several items that are not good and people don't buy.
Investors should not be moving their investment funds to restaurant chains that have menus with higher fat content since there is no data that connects the profitability of a restaurant chain to the fat content of its menu. In fact general observation would tend to show the healthier menus tend to have a higher profit margin due to cost factors.
Some investors make an argument that investing in restaurant chains with fattier menus can be more profitable. Their reasoning is that patrons of such establishments will eat more and more frequently because the foods they eat will cause them to gain weight and thus have greater food cravings. But this is obviously socially very irresponsible, and no decent investor would follow this logic.
A gradual shift in perceptions is required. If effetctive morally responsible advertising is done that focuses people's opinions in favor of healthy eating instead of fast food; the market for healthy foods can increase and hence the sales of healthy products may increase as well. That will ensure the booming of that industry and investors would be more likely to invest in companies that produce healthy or organic food instead of restaurant chains with fattier menus.