This is of importance because obesity is now considered to be an epidemic in many countries, particularly the USA. Indeed, for more than 20 years obesity has been seen as "the most challenging public health problem that we have faced" (Ref. 1). One of the things that is obviously associated with obesity is increasing consumption of energy-rich food; and one of the things implicated in increased consumption is the size of the portions being eaten — increased portions lead to increased energy intake, and if the energy is not immediately used then the person will put on weight.
The relationship between obesity and the size of portions is a complex issue, which I will not go into here. However, for those of you who are interested, there are a number of recent literature reviews (Refs 2, 3, 4, 5, 6, 7). The experimental consensus is that people consistently consume more food and drink when offered larger-sized portions, packages or tableware than when offered smaller-sized versions.
What is of particular interest for this blog post is that health professionals have been collecting data about increasing portion sizes over the years, and I thought that we might look at some of the data, and their consequences. Portion size is usually reported to be largest in the USA, and steadily increasing [Refs 8, 9], although data from Europe show similar trends — eg. Denmark (Ref. 10), the Netherlands (Ref. 11).
Increased portion sizes
People have now realized that there are two ways that increased portions have been happening, the first of which is related to hamburgers and the second of which is related to wine glasses. That is, food is often served as a discrete unit (Ref. 12), either as a single object (eg. a hamburger or a packet of crisps) or as a single serving (eg. a wine glass or a plate / bowl). Both units have been increasing in recent decades.
For hamburgers, Ref. 13 found that a single McDonald's hamburger weighed 1.6 oz when first introduced in 1955 but in 2002 varied in weight from 1.6-8.0 oz, Burger King's weighed 3.9 oz in 1954 but 4.4-12.6 oz in 2002, and Howard Johnson's weighed 3.5 oz in the 1970s and 5.0-8.0 oz in 2002. These are hardly small increases.
This is part of a general trend, in which the sizes of food products sold as a single package have increased through time. The next graph, from Ref. 14, shows the time when a larger unit size was introduced (ie. larger than when the product was first marketed) for a total of 181 different food products in the USA. The increase in portions has been rapid since 1980.
Moving on to the other category, products sold "loose" (rather than in a fixed package size), the next graph, from Ref. 15, shows the capacity of wine glasses available in England over the past 3 centuries. Once again, the increase has been rapid since 1980.
This is also part of a general trend, in which the sizes of other dinnerware have also increased through time. For example, Ref. 16 shows a similar graph of increasing size of dinner plates in the USA over the past century.
Studies of drink consumption
This raises the obvious question of whether increased sizes of glasses has any affect on the amount of alcohol consumed. The general consensus seems to be "yes". Here, I will briefly discuss a few recent experimental studies about the wine glasses, tumblers, etc into which drinks are poured in licensed premises (restaurants and bars), rather than at home.
Several years ago, the authors of Ref. 17 visited a number of bars in California, to check whether the wines, mixed drinks and straight drinks varied in alcohol level based on the size or shape of the glass it was served in (due to variation in the bartender pouring). They concluded that: “Straight shots and mixed drinks served in the relatively large pint glass ... were found to contain more alcohol than drinks served in a short wide glass. No other significant differences were found between glass types.” That is, in this situation wine glass size and shape made no difference.
Later, the authors of Refs 18 and 19 did similar experiments for wine glasses at three bar / restaurants in England. However, in this case the portion of wine served was identical in all cases — the only thing that varied was the size of the wine glass (see the picture above). They found that: “Daily wine volume purchased was [10%] higher when sold in larger compared to standard-sized glasses. This effect seemed principally driven by sales in the bar area ... Findings were inconclusive as to whether sales were different with smaller vs. standard-sized glasses.”
So, serving people in over-sized glasses led them to purchase more glasses of wine. It is worth looking at how this effect is assumed to work. The Delboeuf Illusion is usually considered to be the prime force, as shown in the next picture (from Ref. 16) — the plate on the left looks like it has less food, even though the two amounts are identical. The same is true of the two wine glasses shown above — if it looks like you are drinking less per glass, then you buy more glasses.
This idea was experimentally tested by the authors of Ref. 20, who asked their participants to fill a second glass with the same amount of wine as was present in the first (standard) glass — the second glass was either wider or taller or both, compared to the reference. The authors concluded that: “Participants under-filled the wider glass relative to the reference glass and and over-filled the larger glass relative to the reference glass. These results are broadly consistent with people using the relative fullness of glasses to judge volume, and suggest both the shape and capacity of wine glasses may influence perceived volume.” A similar conclusion was reached by the authors of a similar but much earlier study (Ref. 21).
However, these same authors (Ref. 22) also tested a different idea in the laboratory, that the effect might be produced by differences in drinking behavior — drinking rate, sip number and sip duration might be increased for larger glasses. Sadly, they found that: “Wine drunk from the larger, compared with the smaller glass, was consumed more slowly and with shorter sip duration, counter to the hypothesised direction of effect.” This might be due to the participants drinking alone in a laboratory rather than socially in a bar / restaurant.
However, for lager consumed from straight-sided versus curved beer glasses, the authors of Ref. 23 found that: “Participants were 60% slower to consume the alcoholic beverage from a straight glass compared to a curved glass. This effect ... was not observed for a non-alcoholic beverage. Participants also misjudged the half-way point of a curved glass to a greater degree than that of a straight glass.” So, glass shape mattered.
This inevitably leads us to consider the affect that of all of this research might have on marketing. Because the actual food and drinks are usually only a small percentage of the cost of eating and drinking, giving customers a larger portion is a strategy that might increase total sales. This leads to the widespread practice of “super-sizing” — giving customers a lot more food (and calories) for only a small additional cost. This seems to be the main motivation for sellers increasing their food portions, as described above.
People seem to purchase larger portion sizes than they actually need (in terms of energy), for two main reasons (Ref. 2):
- "value for money" — larger portions are attractive because they offer more value for money, ie. a lower price per unit;
- "portion distortion" — larger portions can be perceived as an appropriate amount to consume on a single occasion, due to continuous exposure to larger food portion sizes.
For alcoholic beverages, marketing has been discussed by Ref. 24, particularly with regard to “strategies aimed at recruiting new young customers, increasing consumption and nudging drinkers towards stronger products ... Particular attention is paid to the size of the glass and how this can best be manipulated to increase sales.”
The authors quote a number of UK trade publications encouraging the use of larger glasses:
Since 1995, the legally permitted measure sizes for wine by the glass in the UK have been 125 ml, 175 ml and multiples thereof ... In 1996, a spokesman from Carlsberg-Tetley brands urged licensees to call 175 ml a “standard” glass and 125 ml “small” ... Similarly, in 2001, licensees were advised that ‘The basic step is to move from 125 ml glasses to 175 ml ... With 175 ml as the standard and 250 ml as the large size, pubs increase both volumes and profits’ ... A 2004 article declares that small glasses ‘give the impression that the pub doesn’t take wine seriously,’ and that ‘getting customers to “go large” in glass size not only improves the experience, it’s also a tremendously efficient way of cranking up profit.’So, it does seem that the drinks business is actively involved in the current obesity epidemic.
There are "standard portions" described for many foods, usually based on daily diet requirements or other health considerations. For example, in the USA these standards are provided by the Food and Drug Administration (FDA), the Department of Agriculture (USDA), and the Centers for Disease Control and Prevention (CDC). These portions are often listed as "standard servings" on packaged food.
Although a "standard drink" is defined in terms of the amount of alcohol it contains, most people have little idea about what constitutes a standard drink in terms of volume, irrespective of whether it refers to wine, beer or spirits. In the experiment conducted by the authors of Ref. 25, almost all of the participants poured a drink that was too large.
Unfortunately, the so-called “standard drink” can vary considerably among countries. For example, in the USA a standard drink contains 14 g (0.6 oz) of ethanol, which would be 150 mL (5 fl. oz) of 12% ABV wine. However, in Australia, the standard drink contains only 10 g of ethanol, which is equivalent to 105 mL of wine. So, a bottle of 12% wine in the USA is considered to contain 5 standard drinks but in Australia it contains 7 such drinks. Obviously, with increased alcohol strengths of wine in recent years there are even more standard drinks per bottle these days!
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