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Environmental influences
Many environmental cues influence food choice and intake, although consumers may not be aware of their effects (see mindless eating). Examples of environmental influences include portion size, serving aids, food variety, and ambient characteristics (discussed below).

Portion size
Portion sizes in the United States have increased markedly in the past several decades. For example, from 1977- 1996, portion sizes increased by 60% for salty snacks and 52% for soft drinks. Importantly, larger product portion sizes and larger servings in restaurants and kitchens consistently increase food intake. Larger portion sizes may even cause people to eat more of foods that are ostensibly distasteful; in one study individuals ate significantly more stale, 2-week-old popcorn when it was served in a large versus a medium-sized container.

Serving aids
Over 70% of one's total intake is consumed using serving aids such as plates, bowls, glasses, or utensils. Consequently, serving aids can act as visual cues or cognitive shortcuts that inform us of when to stop serving, eating, or drinking.

In one study, teenagers poured and consumed 74% more juice into short, wide glasses compared to tall, narrow glasses of the same volume. Similarly, veteran bartenders tend to pour 26% more liquor into short, wide glasses versus tall, narrow glasses. This may be explained in part by Piaget's vertical-horizontal illusion, in which people tend to focus on and overestimate an object's vertical dimension at the expense of its horizontal dimension, even when the two dimensions are identical in length.

In addition, larger bowls and spoons can also cause people to serve and consume a greater volume of food, although this effect may not also extend to larger plates. It has been suggested that people serve more food into larger dishes due to the Delboeuf Illusion, a phenomenon in which two identical circles are perceived to be different in size depending upon the sizes of larger circles surrounding them.

Plate color has also been shown to influence perception and liking; in one study individuals perceived a dessert to be significantly more likable, sweet, and intense when it was served on a white versus a black plate.

Food variety
As a given food is increasingly consumed, the hedonic pleasantness of the food's taste, smell, appearance, and texture declines, an effect commonly referred to as sensory-specific satiety. Consequently, increasing the variety of foods available can increase overall food intake. This effect has been observed across both genders and across multiple age groups, although there is some evidence that it may be most pronounced in adolescence and diminished among older adults.

Even the perceived variety of food can increase consumption; individuals consumed more M&M candies when they came in ten versus seven colors, despite identical taste. Furthermore, simply making a food assortment appear more disorganized versus organized can increase intake.

It has been suggested that this variety effect may be evolutionarily adaptive, as complete nutrition cannot be found in a single food, and increased dietary variety increases the likelihood of meeting nutritional requirements for various vitamins and minerals.

Salience
Increased food salience in one's environment (including both food visibility and proximity) has been shown to increase consumption. Regarding visibility, food is consumed at a faster rate or at a greater volume when it is presented in clear versus opaque containers. Having large stockpiles of food products at home can increase their rate of consumption initially; however, after about a week's time the consumption rate may drop back down to the level of non-stockpiled foods, perhaps due to sensory-specific satiety. It has been suggested that salient foods increase intake by serving as a continuous consumption reminder and increasing the number of food-related cognitive choices an individual must make. Additionally, some studies have found that obese individuals may be more susceptible to the influence of food salience and external cues than individuals with a normal-weight BMI.

Distractions
Distractions can increase food intake by initiating patterns of consumption, obscuring ability to accurately monitor consumption, and extending meal duration. For example, greater television viewing has been associated with increased meal frequency and caloric intake. A study in Australian children found that those who watched two or more hours of television per day were more likely to consume savory snacks and less likely to consume fruit compared to those who watched less television. Other distractors such as reading, movie watching, and listening to the radio have also been associated with increased consumption.

Temperature
Energy expenditure increases when ambient temperature is above or below the thermoneutral zone (the range of ambient temperature in which energy expenditure is not required for homeothermy). It has been suggested that energy intake also increases during conditions of extreme or prolonged cold temperatures. Relatedly, researchers have posited that reduced variability of ambient temperature indoors could be a mechanism driving obesity, as the percentage of U.S. homes with air conditioning increased from 23-47% in recent decades. In addition, several human and animal studies have shown that temperatures above the thermoneutral zone significantly reduce food intake. However, overall there are few studies indicating altered energy intake in response to extreme ambient temperatures and the evidence is primarily anecdotal.

Lighting
There is a dearth of research investigating relationships between lighting and intake; however, extant literature suggests that harsh or glaring lighting promotes eating faster, whereas soft or warm lighting increases food intake by increasing comfort level, lowering inhibition, and extending meal duration.

Music
Compared to fast-tempo music, low-tempo music in a restaurant setting has been associated with longer meal duration and greater consumption of both food and drink, including alcoholic beverages. Similarly, when individuals hear preferred versus non-preferred music they tend to stay at dining establishments longer and spend more money on food and drink.

Presence of others
There is a substantial amount of research indicating that the presence of others influences food intake. In reviewing this literature, Herman, Roth, and Polivy have outlined three distinct effects:

1. Social facilitation – When eating in groups, people tend to eat more than they do when alone.

In daily diary studies, individuals have been found to eat from 30% to 40-50% more while in the presence of others versus eating alone. In fact, some research has indicated that the rate of intake is best described as a linear function of the number of people present, such that meals eaten with one, four, or seven other people were 33%, 69%, and 96% larger than meals eaten alone, respectively. In addition to these observational findings, there is also experimental evidence for social facilitation effects.

Meal duration may be an important factor in social facilitation effects; observational research has identified positive correlations between group size and meal duration,, and further investigation has confirmed meal duration as a mediator of group size-intake relationships.

2. Modeling – When eating in the presence of others who consistently eat either a lot or a little, individuals tend to mirror this behavior by also eating either a lot or a little.

Early studies of modeling effects investigated food intake alone versus in the presence of others who either ate either a very small amount (1 cracker) or a larger amount (20-40 crackers). Findings were consistent, with individuals consuming more when paired with a high-consumption companion than a low-consumption companion, whereas eating alone was associated with an intermediate amount of intake. Research manipulating eating social norms within real-life actual friendships has also demonstrated modeling effects, as individuals ate less in the company of friends who had been instructed to restrict their intake versus those who had not been given these instructions. Furthermore, these modeling effects have been reported across a range of diverse demographics, affecting both normal-weight and overweight individuals, as well as both dieters and non-dieters. Finally, regardless of whether individuals are very hungry or very full, modeling effects remain very strong, suggesting that modeling may trump signals of hunger or satiety sent from the gut.

3. Impression management – When people eat in the presence of others who they perceive to be observing or evaluating them, they tend to eat less than they would otherwise eat alone.

Leary and Kowalski define impression management in general as the process by which individuals attempt to control the impressions others form of them. Previous research has shown that certain types of eating companions make people more or less eager to convey a good impression, and individuals often attempt to achieve this goal by eating less. For example, people who are eating in the presence of unfamiliar others during a job interview or first date tend to eat less.

In a series of studies by Mori, Chaiken and Pliner, individuals were given an opportunity to snack while getting acquainted with a stranger. In the first study, both males and females tended to eat less while in the presence of an opposite-sex eating companion, and for females this effect was most pronounced when the companion was most desirable. It also seems that women may consume less in order to exude a feminine identity; in a second study, women who were made to believe that a male companion viewed them as masculine ate less than women who believed they were perceived as feminine.

The weight of eating companions may also influence the volume of food consumed. Obese individuals have been found to eat significantly more in the presence of other obese individuals compared to normal-weight others, while normal-weight individuals' eating appears unaffected by the weight of eating companions.

Awareness Although the presence and behavior of others can have a strong impact on eating behavior, many individuals are not aware of these effects, and instead tend to attribute their eating behavior primarily to other factors such as hunger and taste. Relatedly, people tend to perceive factors like cost and health effects as significantly more influential than social norms in determining their own fruit and vegetable consumption.

Weight bias
Individuals who are overweight or obese may suffer from stigmatization or discrimination related to their weight, also called weightism or weight bias. There is emerging evidence that experiences with weight stigma may be a type of stereotype threat which leads to behavior consistent with the stereotype; for example, overweight and obese individuals ate more food after exposure to a weight stigmatizing condition. Additionally, in a study of over 2,400 overweight and obese women, 79% of women reported coping with weight stigma on multiple occasions by eating more food.