In 2002, there were more than 1 billion overweight people worldwide and over 300 million of these were obese. This problem is not limited to developed countries as evidenced by some of the following prevalence rates of obesity. A survey carried out during 1991-1994 in the urban region of Cairo, Egypt, (in a general population over 20 years of age) found that 56.0% of men and 45% of women were obese (body mass index. In Saudi Arabia, 26.4% of men and 44.0% of women in a nationally representative survey of adults over 30 years of age (in 1995œ2000) were found to be obese; equivalent to 35.6% of the population. In a survey conducted from 1998 to 2000, Kuwait was found to have a slightly lower prevalence of obesity; 21.5% in men and 22.8% in women. A study from India reported that 25.4% of men and 35.8% of women, over 20 years of age, were overweight in 2000. In a report from Japan, 26.8% of men and 21.3% of women were overweight. The highest percentage of obesity was found in the population in Japan aged between 60 and 69 years, with 30.7% for men and 31.0% for women from a nationally representative survey of adults carried out in 2000.
In 1999 in Mongolia, the prevalence of overweight people for the population over 20 years of age was 52.0%; 44.0% for men and 57.0% for women. China has some of the lowest reported prevalence rates of obesity with 1.7 -2.9% for men and 4.3% for women in the population aged 20 to 45 years. Thailand is reported to have a prevalence of a in 18.8% of men and 28.6% of women aged 13 to 59 years. A study from Italy, carried out in 1998, reported 18.0% of men and 22.0% of women (aged 35œ74 years) to be obese in a nationally-representative sample. South Africa was found to have very different prevalence rates by sex; 9.3% of men and 30.1% of women (more than 15 years of age) were reported obese in a survey carried out in 1998. In Ghana, the prevalence of overweight women aged 15œ49 was found to be 16.1%, reaching 21.7% in the group aged 35œ39 years old. In a study conducted in Germany in 1998, 20.3% of the population, aged 18œ79 years, were reported to be obese.
Given this global prevalence of persons who are overweight and obese, effective dietary strategies are needed for both losing weight and maintaining a healthy body weight. Most strategies emphasize the macro nutrient composition of the diet, and many researchers have investigated the effects of macro nutrient content on satiety (the effects of a food or a meal after eating has ended), food intake, and body weight. Given the research focus on macro nutrients, this review examines the influence of particular food groups on intake and body weight, and evaluates whether laboratory and clinical interventions, as well as epidemiologic investigations, have shown that consumption of fruit and vegetables affects satiety, food intake, and body weight.
Because many studies mention fruit and vegetable consumption, five criteria were established for including them in this review:
- they must be studies in adults or children that can be regarded as either interventions or epidemiological investigations related to fruit and vegetables and weight management;
- they must not report on an intervention limited to an exclusively vegetarian diet;
- they must provide specific data on intake of fruit or vegetables;
- they must report the effects of the intervention on satiety, energy intake, body weight, or BMI;
- they must be published in a peer-reviewed journal.
There was no limitation of the types of participants in the studies, as all studies of free-living persons of both sexes were included. Animal studies were not included as none were identified which met the criteria. Only papers reported in English were considered. Peer-reviewed journal articles published between January 1966 and July 2003 which included an investigation of fruit and vegetable intake and body weight in adults and children and that reported a test for significance are included. Articles were identified by searching
MEDLINE, PubMed and Web of Science using the following keywords: energy balance, treatment of obesity, weight control, weight loss, weight reduction, energy density, satiety, fruit and vegetable consumption, orosensory factors, water incorporated into food, volume of food, glycaemic (glycemic) index, energy balance, vegetarian diets, dietary fibre (fibre), hunger, time-calorie displacement, metabolizable energy, caloric ratio, weight and BMI. Additional articles were collected by examining the reference lists in the original research articles. Although every effort was made to be comprehensive, studies may have been overlooked because the relevant measures were secondary outcomes that would not be identified in a literature search.
Firstly, the review considers in manner in which fruit and vegetables affect regulation of energy intake, and secondly, intervention and epidemiologic studies that have tested the effects of these foods on intake regulation and body weight. Although little research has addressed directly the effects of fruits and vegetables on these variables, a number of studies have done so indirectly.
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