In this article of our series, we continue to clarify what can lead to a successful diet, examining three of the most important properties of foods that can lead to overeating.

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Although the dietary influences on consumption are numerous and complex, including factors such as food composition, form, cost, palatability, the rate at which we eat and availability, in this article we will focus on studies that support three of the most powerful of these nutritional influences: portion size, energy density and variety.

PORTION SIZE

In a "real world" experiment conducted in a restaurant, the portion of a popular pasta dish was covertly varied by 50% on different days and consumed more when the available portion was larger, with no differences in the evaluation of the appropriateness of portion sizes. In another study, increasing the portions of all meals, snacks and drinks served to men and women for two days led to a sustained increase in energy intake. In an even larger cross-sectional study, over 11 days, the portion size of all food and drink served increased by 50%. Although participants had ample time to perceive and compensate for excess energy intake, this did not occur over time in this study. Multiple studies have also shown that the uptake of children in routine childcare settings varies according to the quantity served to them.

ENERGY DENSITY

The effect of macronutrients and energy density (i.e. the amount of calories provided by a meal) can be dissociated by varying the water content of the food. This operation changes the energy density without impacting on the macronutrients or the total energy provided, an approach that has been applied to many studies.

Similarly with older studies, in a recent study, when the amount of dietary fat was covertly manipulated in all available foods, while energy density was kept constant by varying the proportion of water or water-rich vegetables or fruits, participants ate a constant weight of food regardless of the levels of dietary fat content served to them.

More support for the role of energy density in determining intake comes from studies in which energy density was modified while macronutrient ratios remained constant. For example, one study covertly changed the energy density of all available foods by up to 30%, while maintaining a similar macronutrient composition. While access was free, participants eventually ate a constant food weight, i.e. energy intake was directly altered by the energy density of the food. The higher the energy density of the diet, the more energy participants consumed during the two days of the trial period.

It is worth noting that the energy density of solid foods is the strongest and most reliable determinant of energy intake and body weight. That is, drinks and soft drinks affect the regulation of food intake in a different way to solid foods, and accompanying a meal with a soft drink will have quite different effects from changing the energy density of a meal using water-rich fruits and vegetables.

VARIETY

Sensory satiety promotes the consumption of a variety of foods and helps to ensure the nutritional balance of the diet. However, in the context of today's food environment, variety can contribute to overconsumption.

In a series of experiments, it was shown that sensory satiety can influence meal intake. For example, participants ate more over four courses when sandwiches with different fillings were offered in each course than when sandwiches with the same filling were offered. It was also found that more was consumed when yogurts that differed in taste, appearance and texture were offered compared to offering only the favorite yogurt flavor.

It has also been found that the effects of dietary variety are observed even in meals consisting of the same food when differences in sensory characteristics are introduced. For example, in one study energy intake increased in response to the offer of pasta with multiple shapes as opposed to a single shape or candy presented in multiple colours as opposed to one colour.

The presentation of a new, palatable food often reinstates eating, even in conditions of satiation even in saturation conditions. Even small differences in the sensory properties of food can cause this phenomenon that can be caused by variation in energy intake, although the effects are stronger when foods differ significantly, e.g. sweet versus savory.

In summary:

• A larger portion of food (regardless of the size of the plate) means more food consumption.
• Greater energy density (the amount of calories provided by a meal) means more food consumption. Changing the energy density of a meal by using water-rich fruits and vegetables can help a lot.
• More variety of food in a meal means more food consumption.
• By combining these three parameters, serving a variety of vegetables can increase vegetable consumption, which can be used to reduce energy intake and manage weight.

-Suprastratum: The authority on health, fitness and nutrition

Sources/bibliography/more reading:

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