Why Are We Overweight? Part 10

In a perfect world, humans would have the instinctive ability to eat the right amount of food and be as active as we need to be in order to keep our body fat level close to that which is ideal for health. If this were the case, homeostatic regulation would be in effect much like the processes that maintain our body temperature are controlled with nary a conscious thought on our part. Interestingly, there is a hormonal system designed to make us want to eat and be active (to find food) when we are in a negative energy balance and eschew these behaviors when our ledger is in the black. And this homeostatic drive is likely responsible for the fact that most animals carry what would be considered a characteristic (ideal) amount of body fat for their particular species.

Homeostatic regulation of energy balance (and, by extension, body fat accumulation) becomes confounded in humans because factors other than energy balance dictate how much energy we choose to ingest. For example, in addition to simply eating to survive (i.e., maintain intake/expenditure equilibrium), we eat for pleasure, to cope with stress and out of habit. Modern man also takes in a lot of energy in liquid forms, which goes against what the system is designed for. Furthermore, we don’t have to expend much energy to procure food. The end result is that instead of the prevailing negative energy balance upon which the homeostatic system is based, we are often in a positive balance, which promotes inactivity. Add in continuing to ingest more than we need for the aforementioned reasons and it’s easy to see why overweight is at epidemic proportions.

The take-home message is that because of how we have evolved, we can no longer trust our instincts when it comes to deciding how much to eat and how active to be. Instead, we must make calculated decisions and this requires understanding how much energy we ingest and expend on a daily basis. Last installment, I explained how the first step is knowing the calories you need to maintain your current body fat stores. This is called your caloric maintenance level and can be determined through trial and error (i.e., ingesting the same amount of calories each day for a couple of weeks, keeping expenditure relatively constant and finding the intake level at which your weight does not fluctuate). Once you know this value, you can then decide how to shift the balance in favor of fat loss.

To exemplify, consider a person looking to lose fat who currently needs 2500 calories each day to stay as they are. Theoretically, 3500 calories of energy are contained in a pound of fat, so a shift toward expenditure to the tune of  500 calories per day should facilitate the loss of a pound each week. With this in mind, the person would then determine how they intend to put such a deficit in place. Energy expenditure is a function of basal metabolic rate (the amount of energy we expend to simply exist), energy expended in all daily activities and energy required to digest food. Basal metabolic rate is primarily determined by genetics, but is also influenced by the amount of muscle we carry. However, while it’s nice to envision simply adding enough muscle to establish the deficit while leaving everything else constant, this is rarely realistic, especially if you’ve already been training with weights and are close to your genetic potential. Furthermore, even in cases where it might be possible, some people might be adverse to carrying that amount of extra muscle. So, generally speaking, a more realistic objective is to perform resistance training regularly to ensure that you’re not losing muscle (and the associated metabolic activity) and then consider any additional muscle you put on to assist your efforts as icing on the fat-loss cake.

If manipulating muscle is not a major factor in establishing a negative energy balance, there are two other alternatives: You can reduce the calories you ingest and/or increase the amount you expend during all of your daily activities. With respect to the latter, aerobic exercise is particularly well suited because you can work for an extended period at a relatively high energy turnover while also improving your conditioning level. Improved fitness will allow you to maintain even higher work rates in the future and this is important because energy use per unit time is directly related to the work rate at which you are exercising.

Establishing an energy deficit for fat loss solely by increasing activity level (and, therefore, not having to reduce intake below what used to be your caloric maintenance level) is advantageous because it ensures that your body is less apt to adjust its metabolism in response to a perceived threat to survival (i.e., enter the so-called ‘starvation mode’). What is more, it’s important to maintain caloric intake as high as possible to keep the intake-reduction option open for down the line. Finally, a greater number of calories ingested also makes it easier to satisfy your nutrient requirements, which can be determined based upon your lean body mass (e.g., grams of protein per kilogram) and/or the total amount of calories you consume (e.g., as a percentage according to USDA dietary reference guidelines).  

This article was originally published in New Living Magazine, which can be accessed on-line at www.newliving.com.






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