Evidence Implicating Eating as a Primary Driver for the Obesity Epidemic

Abstract

This article addresses the extent to which increases in energy intake as opposed to decreases in energy expenditure are driving the obesity epidemic. It argues that while both intake and expenditure are plausible and probable contributors, the fact that all intake is behavioral, whereas less than half of expenditure is behavioral, makes intake a conceptually more appealing primary cause. A review of per capita food disappearance trends over time and of trends in individual intakes is presented to support the plausibility of this perspective. Increases in energy intake mirror increases in body weight quantitatively and are equally widely distributed across diverse groups within the larger population. Diabetes 56: [2673][2674][2675][2676] 2007 O besity is the number one nutritional issue in the U.S. and in much of the rest of the world today. More than two-thirds of U.S. adults have body weight exceeding recommended ranges, putting these individuals at increased risk for a variety of adverse health outcomes (1-3). Compounding concern about high rates of population obesity is the fact that obesity prevalence rates are rising rapidly. The proportion of the population affected by obesity has more than doubled in the last 20 -30 years, the rate of increase holding steady at approximately one percentage point per year. So far, there is no evidence to suggest that the obesity trend will slow any time soon. The rapid increase in obesity rates is why it is now often called an "epidemic," and both scientific researchers and public health officials are energetically seeking answers to two closely related questions, i.e., what is causing it, and how can we reverse it?Conceptually, obesity is a state in which an individual has stored body fat in amounts far exceeding biological need. Usually it is a result of a small but chronic positive energy imbalance that continues over many years. The reason why the problem is so widespread and why it suddenly worsened dramatically starting around 1980 is not well understood. We know where energy comes from, i.e., food. We also know how the body uses it. More than half is used to perform obligatory biological functions, such as maintenance of body temperature, metabolism, and tissue repair. The rest is used to power the muscular work required for human beings to interact with their environment. If food energy intake exceeds energy requirements, excess energy is stored as body fat. If energy expenditure exceeds energy intake, energy fat stores are tapped to make up the difference. Changes in the rate at which body fat is accumulated over time are thus intimately linked to patterns of food intake and physical activity.In trying to understand the evolving obesity epidemic, the relative contribution of declining energy expenditure and increasing energy intake to the problem has yet to be determined conclusively, and there is disagreement among health professionals about the importance of the two (4 -6).

The growing Canadian energy gap: more the can than the couch?

“…These results are consistent with those from Harnack et al and Jeffery and Harnack, which showed that energy 2 0 0 0 2 0 0 1 1 9 9 8 1 9 9 9 1 9 9 6 1 9 9 7 1 9 9 4 1 9 9 5 1 9 9 3 1 9 9 2 2 0 0 3 2 0 0 1 1 9 9 7 1 9 9 9 1 9 9 3 1 9 9 5 1 9 8 9 1 9 9 1 1 9 8 7 1 9 8 5 1 9 9 1 1 9 9 0 1 9 8 9 1 9 8 8 1 9 8 7 1 9 8 6 1 9 8 (1985)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003) availability in the US food supply increased by 15 % between 1970 and 1994 (31) and by 22 % between 1982 and 2004 (32) . Results are also consistent with Bleich and colleagues, who have modelled the fraction of obesity due to energy in and energy out for a number of developed countries (10) .…”

Effect of acute and chronic caloric restriction and metabolic glucoprivation on spontaneous physical activity in obesity-prone and obesity-resistant rats

“…food deprivation; locomotor activity; diet-induced obesity THE RISING PREVALENCE OF OBESITY indicates that a sustained positive imbalance between energy intake and expenditure exists at the population level. However, it's unclear which factor, excessive intake or reduced energy expenditure, has contributed more to the obesity epidemic (19). Given the strong influence of genetics and environment on body weight gain, it's intriguing that spontaneous physical activity (SPA) has a strong familial and genetic component (65) and that lean adults and children display greater SPA than their obese counterparts (25,38).…”

Mechanisms behind early life nutrition and adult disease outcome

“…The reasons behind this epidemic are not clearly understood, however this metabolic disease can result from a complex interaction between many factors including genetic, physiological, behavioural and environmental influences. The rate at which this disease has increased suggests that environmental and behavioural factors such as increased consumption of high-fat and high-energy foods, coupled with reduced physical activity play a greater role than genetic causes [2][3][4] . It is therefore particularly relevant that recent epidemiological and animal studies have suggested that long-term health can be influenced by events in fetal and early infant phases of life.…”