Nutritional Requirements Throughout the Life Cycle

Excess Calorie Intakes: A Risk Factor Common to All Age Groups

The major nutritional problem encountered in developed countries is excess macronutrient intake (especially saturated fat, protein, and sugar) and insufficient intake of the fiber and micronutrients provided by vegetables, fruits, grains, and legumes.

Overnutrition begins early. Pregnant and lactating women are encouraged to eat more because they are “eating for two.” While it is true that an expectant mother must provide nutrition for both herself and her developing baby, the increased energy requirement of pregnancy amounts to no more than about 300 calories per day.¹ Excessive nutrient intake may result in excessive weight gain, conferring a greater risk for cesarean section and other complications of pregnancy and delivery.⁸

Overfed infants and children may develop dietary habits and perhaps even metabolic characteristics that have lifelong consequences.^9,10,11 Higher–than–recommended energy intakes at 4 months of age have been shown to predict greater weight gain before 2 years and risk for obesity in childhood and adulthood.^{12, 13} Therefore, caretakers should select foods conducive to healthy body weights and restrain their desire to promote child growth through overfeeding. 

Adolescents face a similar problem. Many teens consume higher–than–recommended amounts of fat, saturated fat, sodium, and sugars, thereby increasing the risk for adolescent and adult obesity, among other health problems.¹⁴ The increased prevalence of excess body weight in adolescents is correlated with escalating risk for type 2 diabetes in this population.¹⁵ This does not mean that adolescents are well nourished, however. In spite of their higher energy intake, adolescents frequently fail to achieve required intakes of essential micronutrients (eg, vitamins A and C).¹⁶ This problem is compounded by the fact that roughly 60% of female and more than 25% of male adolescents are dieting to lose weight at any given time, and between 1% and 9% report using maladaptive habits, such as purging, to do so.¹⁷

Adults in developed countries are at particular risk from excess energy intake. While a significant percentage of Americans (5% to 50%) consume less than half the recommended intake of micronutrients,¹⁸ energy balance is typically far in excess of needs. In Western countries, dietary staples (eg, meat, dairy products, vegetable oils, and sugar) are more energy dense than in traditional Asian or African cultures, where grains, legumes, and starchy vegetables are larger parts of the diet. This problem is aggravated by increases in food portion sizes and in the availability and consumption of calorie–dense, nutrient–poor fast foods.¹⁹ As a result, this age group is experiencing an epidemic of obesity–related diseases, including coronary heart disease, hypertension, diabetes, and cancer. Metabolic syndrome, often triggered by obesity, is a common problem in elderly persons, one associated with greater risk for premature mortality.²⁰ These circumstances indicate a need for diets that are micronutrient dense, while modest in fat and energy.