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Being overweight may make you lazy

Harold Mandel's picture
An overweight lazy woman

It often appears that overweight people are unusually lazy and yet it is wrong to assume this is why they weigh too much. In other words we are often lead to think that someone who is basically sedentary and lazy will become overweight and not the other way around. New research shows that being overweight may in fact be a major causative factor in making people lazy.

Research which was done on rats shows that a refined low-fat diet induces obesity while impairing performance on a progressive ratio schedule of instrumental lever pressing by rats, reports the journal Physiology & Behavior. In rodents purified high-fat diet (HFD) feeding causes harmful metabolic and cognitive effects in comparison with unrefined low-fat diets.

These effects are generally attributed to the refined diet's high content of fat. There has been less attention paid to other mechanisms which are associated with the extremely refined state of the diet. Although the effects of HFD feeding on cognition have been investigated there has not been much known about the impact of refined vs. unrefined food on cognition. Researchers decided to test the hypothesis that a refined low-fat diet (LFD) increases body weight and therefore adversely affects cognition in comparison to an unrefined diet.

The researchers observed that after six months the rats on a purified low-fat diet (REF) gained significantly more weight than the rats fed unrefined rodent chow (CON). It was observed that REF rats made significantly less lever presses than CON rats. This indicated that there was a chronic lowering of motivation for instrumental performance in the REF rats.

The researchers concluded that diet-induced obesity produces a significant deficit in the motivated behavior of rats, which is independent of dietary fat content. This implies there may very well be an association between obesity and motivation. The researchers think this shows that behavioral traits which are comorbid with obesity, such as depression and fatigue, may be due to effects of obesity instead of being contributing causes.

This new University of California psychology study offers evidence that being overweight is responsible for making people tired and sedentary, instead of the other way around, reports UCLA in a discussion of this research. Scientists who were led by UCLA's Aaron Blaisdell placed 32 female rats on one of two diets for six months. The first diet was a standard rat's diet which consisted of relatively unprocessed foods such as ground corn and fish meal. The ingredients which were in the second diet were highly processed with substantially more sugar. Essentially the lower quality second diet was a junk food diet.

The researchers observed there was a significant difference in the amount of weight the rats had gained after just three months. The 16 rats on the junk food diet had become noticeably fatter. Blaisdell, who is a professor of psychology in the UCLA College of Letters and Science and a member of UCLA's Brain Research Institute, said, "One diet led to obesity, the other didn't." Blaisdell said the experiments which the researchers performed also suggest that fatigue may result from a junk food diet.

During this study the rats were given a task in which they were required to press a lever in order to receive a reward of food or water. It was observed that the rats who were on the junk food diet demonstrated impaired performance. These rats took substantially longer breaks than the lean rats did prior to returning to the task. During a 30-minute session, the overweight rats took breaks which were about twice as long as the lean rats.

Blaisdell has pointed out that overweight people are often stigmatized as being lazy and lacking discipline. The results from this study suggests to these researchers that the idea which is commonly portrayed in the media that people become fat because they are lazy is not right. The data from this study have suggested that diet-induced obesity is actually a cause, instead of an effect, of being lazy. It appears to the researchers that either the highly processed diet causes fatigue or the diet causes obesity which than causes fatigue.

It is Blaisdell's belief that the findings in this study probably apply to humans. Humans have physiological systems which are similar to rats. Blaisdell says junk food diets make humans and rats hungrier. Furthermore, the researchers observed that the rats who were on the junk food diet developed large numbers of tumors throughout their bodies by the completion of the study. The rats who were on the more nutritious diet had fewer and smaller tumors which were not as widespread.

Blaisdell has pointed out that we are living in an environment with poor quality diets and highly processed foods along with sedentary lifestyles which is very different from the one we are adapted to via human evolution. He sees that difference as leading to many of the chronic diseases which we see today, such as obesity and diabetes. To show his conviction to this reasoning at 45 years old Blaisdell has changed his diet to eat what our human ancestors ate. He now avoids the following foods:

1: Processed food

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2: Bread

3: Pasta

4: Grains

5: Food with added sugar

Instead he now eats a diet consisting primarily of

1: Meats

2: Seafood

3: Eggs

4: Vgetables

5: Fruits

Blaisdell says his new diet has been associated with dramatic improvements in both his physical and mental health. He says he is more full of energy throughout the day and that his thoughts are clearer and more focused than previously.

There is no doubt about it that people who are overweight generally appear to be lazy. An understanding that being overweight may very well be the primary causative factor in the development of dangerously sedentary lifestyles should help people understand the vital significance of maintaining a healthy weight. Sedentary lifestyles can be associated with an increased incidence of a myriad of serious health problems such as hypertension, heart disease, diabetes, cancer, anxiety and depression. This can also of course also lead to even further problems with weight control.

Physicians and other health care professionals should therefore take the time to carefully counsel their patients about why it is more important than ever understood to maintain a healthy weight. Think how rewarding it could be for anyone who is overweight to shed that image of a fat, lazy person who is destined for failure in life and instead take on a new image of a trim, fit, active person who is destined to succeed in life.