A diet low in energy density is recommended in the Dietary Guidelines for Americans and by most nutrition scientists. Energy density is the amount of calories per gram in a food. (here are 2 past posts written about energy density and the DGA)
It best to fill our plates with foods that contain less than 1 calorie per gram, with a few exceptions. Lean proteins (e.g., peanut butter, fish, legumes), whole grains (e.g.,wheat flour, bulgar, quinoa) and mono/poly unsaturated fats and omega 3 fatty acids (e.g., olive oil, salmon) have 2 to 3 calories per gram. More commonly, foods with high energy density are composed of unhealthy solid fats (trans fats and saturated fats) and sugar. On average, meals prepared away from home are higher in energy density than meals prepared at home. This is likely due to the frying, sauteing and use of sauces, condiments and sugars (and red meat; beef and pork).
The quality of a person's overall diet can be assessed based on its adherence to the Dietary Guidelines and its energy density. This is usually done with the Healthy Eating Index or the Alternative to the Healthy Eating Index. Read more about them here.
A majority of Americans, Britains, Australians, Mexicans and such have diets that are poor or need improvement based on the indexes.
While reading a report from the US Economic Research Service (Variyam, 2005), I came across a chart that combined these factors. The findings were quite telling. People who were classifed as having a good diet spent more money eating away from home than those with diets lesser quality diets (poor or needs imrovement). However, the people spending less money on meals away from home were actually consuming MORE of their daily calories from those meals. They also ate meals that were higher in energy density than the good diet group both away from and at home.
You can draw your own conclusions, but here was my take away:
The cheapest foods have the most energy density. A grilled fish dinner with steamed vegetables will have lower energy density than a burger and fries or fried chicken and mashed potatoes and the fish dinner will cost several dollars more. Less money spent, worse food consumed. Those who get more of their calories from away from home foods have higher energy density and poorer diet quality.