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Energy Balance and Body Weight Regulation

The following article summarizes a recent research article published on the Gatorade Sports Science Institute website (gssiweb.org). 

 

Key Points

  • Excess energy (food) intake results in energy storage (fat gain).  A deficit will lead to a reduction in body fat. 
  • While dieting, individuals rarely lose the amount of weight predicted.
  • This can best be explained by changes in metabolic rate due to changes in food consumption, and should be factored into the weight loss equation.
  • Diet and exercise are necessary for long-term weight loss.  Crash diets invoke metabolic adaptations such as decreased resting energy expenditure, reduced levels of satiety hormones, and increased hunger hormones.  These changes antagonize the efforts toward weight loss.  Regular exercise remains the major predictor of long-term weight loss maintenance.

 

Factors Affecting Energy Balance

The factors that regulate human energy intake and expenditure are many and complex.  The biological drive to eat is affected by the hypothalamus and chemical signal from the nervous system.  These "biological" signals are coordinated with psychosocial factors (culture), behavioral factors (snacking during tv commercials), and environmental factors (serving size).  The resulting drive to eat stems from the complex integration of many internal and external factors.

 

[The components of total daily energy expenditure in a person who exercises.]

 Resting energy expenditure is the largest contributor to metabolism for most people.  This is affected by body size, specifically lean body mass.  Additional fat mass also increases metabolic rate, but not nearly as much as lean mass. 

 

A pound of fat equals 3,500 calories.  While it seems logical that cutting 500 calories per day should result in a pound of fat loss per week (7 days x 500 calories = 3,500 calories), this is not necessarily the case.  Research has shown the following points;

  1. Weight loss and weight gain is highly affected by individuality.  In studies with identical twins and studies with random strangers, participants were overfed for a given time period, weight gain was as much as 10 fold different among participants.
  2. Many studies that require participants to self-report calorie intake show that individuals frequently underestimate the actual amount of calories consumed.
  3. It is assumed that as individuals lose weight, it is primarily fat weight.  The truth is that during underfeeding, lean body mass is reduced and the body may decrease its metabolic rate as a protective mechanism. 
  4. Humans are more prone to weight gain than weight loss.  During overfeeding, many factors affect metabolism, including genetic.  While genetic factors play a role in energy balance, the exact nature is unknown. 
  5. In response to reduced calorie diets, the body decreases metabolism and increases hunger, typically associated with weight regain.

 

Weight Loss Tips

No single approach works for everyone. 

  1. Establish realistic long-term goals.  Discard using mirrors as milestones for progress.
  2. Calories do count.  To lose weight you must expend more than you consume.
  3. Change your standards; create lifestyle changes. 
  4. Moderation is key.  In general, the longer and more consistently you lose weight, the longer it will stay off.  If you are attempting to lose weight, create a small calorie deficit (200 calories per day) by making smarter food choices or reduced serving sizes, as opposed to cutting out meals.  For example, drinking water or a diluted fruit drink is an easy way to make minor dietary changes.
  5. Get moving.  Get at least 30 minutes of vigorous activity at least 5 days per week.  Also, park further away from buildings, take the stairs, carry your groceries from the supermarket, etc. 
  6. Strength training can attenuate decreases in metabolism during periods of reduced calorie consumption.  Visit the Personal Training website for more information on scheduling a free personal training appointment.

 

For more information regarding nutrition, visit the Gator Well website; http://www.shcc.ufl.edu/gatorwell/nutrition/nresources.shtml.  This is an excellent resource for nutrition information.  UF students can also meet with a registered dietitian for free, instructions can be found through the above link.

 

 

 

 

Melby, S & Hickey, M. (2005). Energy Balance and Body Weight Regulation, Sports Science Exchange 99, 18 (4). 

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