Years ago, I ran a full-exercise physiology or metabolic lab for a large medical practice. The lab was responsible for conducting tests on a wide variety of individuals; one of the metabolic measurements always included the amount of oxygen an individual utilized during the exam, either exercising or at rest. The measured oxygen uptake directly reflects the number of calories an individual utilizes per minute of an activity. As an example, you burn roughly five calories for every liter of oxygen you use. Since I could directly measure oxygen uptake, I was able to determine the number of calories any specific patient could realistically burn during exercise at a level they could comfortably sustain for an hour. I became very familiar with the physiological dilemma and frustration many have in their effort to lose weight.
The Unfit Adult
The average unfit adult will burn 100 calories walking one mile. Most adults walk at a 3.0 mph pace, so most adults could cover three miles in one hour of walking or burn 300 calories (100 calories × 3 miles). Unfortunately, a pound of body fat contains 3,500 calories, enough to theoretically cover 35 miles (3,500/100). So that one hour of walking does not dramatically affect your total body fat content that day. Walking one hour every day would result in burning 2100 calories – roughly 2 Big Mac Combo Meals. Walking for an hour per day will add up and make a dramatic long-term impact of about 10 pounds over a year. But the day-to-day or week-to-week changes often discourage many obese individuals in their effort to shed a few pounds.
For any real hope for significant weight loss, there must also be a reduction in food intake, by roughly 500 calories per day, for most previously sedentary adults. That 500 reduction in calories per day would add up to 3,500 per week, a pound of body fat. When included with that daily hour of walking, it would result in a 1–2 pounds per week fat loss for most. This may not seem like much, but this is where the patience and discipline issues come into play. Over a year, this could result in a significant weight loss, theoretically 52 pounds or more.
A thin, deconditioned adult does not normally find movement difficult or uncomfortable, just slow due to their deconditioning. Exercise, like that daily walking, requires a reasonable effort. However, the more overweight an individual, the more physically uncomfortable they are with any movement — often, even walking can be uncomfortable. Consider being asked to spend an hour daily doing something that is physically uncomfortable the entire time. How long do you think most individuals are going to be able to discipline themselves to continue? This is an issue most obese contend with, in addition to the chronic lethargy excessive weight precipitates. Excess weight essentially steals your energy levels and, for many, their ability to be physically productive.
For the deconditioned, overweight individual with no or very limited athletic skills, it becomes clear within a week or two how challenging weight loss can be. It should also be pointed out that the more obese the individual is, the more unlikely that long-term positive results will be obtained. This makes these individuals easily victimized with unrealistic weight loss schemes.
You can see why commercial weight loss programs which promise unrealistic results without mentioning the effort and discipline involved are so popular.
The Fit but Slightly Overweight Adult
The calories one burns while exercising for one hour can range from roughly 300 calories to 1,200 calories per hour for someone young and well trained. This fact illustrates why those who stay conditioned have so much more latitude in the amount and types of foods they can consume without becoming overweight. They have “discretionary” calories. When these individuals become slightly overweight and wish to reduce back to their baseline, they can do so more efficiently than their sedentary, obese counterparts.
The ease of weight loss for some and cultural memes often create disdain towards the obese – fat shaming. Most obese adults were obese as children because they never learned good nutritional and exercise skills. They find themselves in a pickle, so to speak, reaching adulthood with the desire to change but without the physical and cognitive skills to make any but very slow progress towards their goal.
The normal-weight adult does not understand that as fat mass begins to shrink in size, the fat cells send out a hormone, ghrelin, to stimulate appetite and replenish what was lost. For a modestly overweight adult, this mechanism of physiologic “nagging” to eat more can be overridden, with disciplined eating, in a few weeks to a couple of months. However, for the obese who may require years of significant lifestyle changes and reduced food intake, this “nagging” to consume more is hard to suppress for such a long time. It is quite an accomplishment for someone who is obese to trim down to a healthier weight and keep it off long term—bravo to you.
The Takeaway
Most of us have the following misconceptions which inhibit effective weight control:
- Just how efficient our bodies are in producing a significant amount of work with few calories.
- Most overestimate their caloric needs, both at rest and during exercise.
- The significant differences between the fit and unfit individuals' abilities to expend calories during exercise.
- A high level of perceived exertion is not necessarily an accurate gauge as to the calories used.
- The duration of an activity is as important as the intensity of it. For most of us, high intensity and short duration is not as beneficial as moderate intensity for longer periods.
- Extreme caloric reduction reduces metabolism and inhibits long-term weight reduction.
- As fat mass declines, many will find it very difficult to contend with the increased hormonal urging to eat to curtail it.
