What Nutritional Factor Has the Greatest Effect on Weight Loss?

Weight loss is probably the most common health and fitness goal and there are so many different products and programs promising to help people shed unwanted pounds, that it is virtually impossible to keep track of them all. While no single diet or nutritional program works for everyone, some are definitely better than others.

Hopefully this is obvious, but any good approach to long-term weight loss must involve nutrition and any product or program that promises weight loss without addressing nutritional issues is almost certainly a gimmick and a waste of money.

The good news is there are many effective weight loss programs. Interestingly, even though some of these programs involve very different eating habits, many of them have similar fundamental strategies at their core. Some of the more popular strategies involve minimizing insulin level fluctuations, eating natural (unprocessed) foods, eating small meals throughout the day, etc.

Many factors influence whether or not a weight loss program will be successful, but some things have been shown to be more important than others. One commonly studied factor is the percentage of calories consumed from fats, protein, and carbohydrates, which is known as the macronutrient profile.

The macronutrient profile is one of the most obvious differences between nutritional programs and diets, with different programs focusing on things like minimizing carb intake, minimizing fat intake, or having a balance between all three. Many programs suggest theirs is best because of the particular macronutrient profile, but it turns out this is not the most important part of a weight loss program.

When it comes to weight loss, the number of calories consumed is more important than what type of calories consumed. Of course, the type of calories you consume is very important for overall health, but eating to improve health and eating to lose weight is not always the same thing.

If weight loss is the primary concern, the number of calories is more important than the macronutrient profile, but there is something else that is even more important. The most important nutritional factor for weight loss is called caloric density or energy density. Caloric density is a measure of how much a food weighs compared to how many calories it contains. Simply stated, foods that weigh more and have fewer calories are better for weight loss.

Researchers have found that most people eat a similar total weight in food every day, regardless of how many calories are contained in those foods¹. Therefore, if two people with similar appetites each eat a pound of food, they should both feel equally full, even if one person ate twice as many calories as the other person.

It is worth noting that, while caloric density does not measure where the calories come from (fat, protein, carbs), foods with good caloric density scores usually have healthy characteristics. This is because many healthy components of food, such as water and fiber, have weight but do not add calories, so they improve caloric density. On the other hand, foods that are very high in fat have low caloric densities, because fat has more than twice the number of calories per weight than protein or carbs.

By looking at the things that influence caloric density, we can see that while it does not directly measure calorie content or macronutrient profiles, caloric density is essentially a partial measure of both things. Another interesting thing is many foods with the best caloric density scores are vegetables, which are considered good foods to eat in virtually every nutritional program or diet.

It is important to note that eating foods just based on their caloric density does not guarantee you will have a well balanced diet. You still need to include some fat, particularly healthy fats (omega-3 oils), and quality protein if you want to lose weight and eat healthy at the same time.

Finally, while caloric density and nutrition in general are very important, they are not the only important things for weight loss. The most successful programs always incorporate both nutrition and exercise. Following a nutrition program that focuses on eating a well-balanced combination of foods with good caloric densities should result in weight loss, but your results will be significantly better if you consistently exercise as well.

1. Savage JS, et al. Dietary energy density predicts women's weight change over 6 y. American Journal of Clinical Nutrition. 2008;88:677.

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