According to a recently published study by the American Journal of Clinical Nutrition (AJCN), acute calorie counting may increase appetite which hinders weight loss. The crossover study subjected male volunteers to two different experimental conditions in the hope to decrease their overall weight. One of the approaches used was to reduce calories by calorie counting in their food while the other was to expose the volunteers to aerobic exercise; both methods were designed to decrease calories by 25%.

Restricting energy consumption through diet was found to have a negative impact on weight loss efforts, as changes in appetite led to overeating. Meanwhile, the study confirmed that exercise alone is more effective in regulating diet for weight loss.

Today, 77% of Americans are trying to lose weight in one way or another, and 69% of them are restricting the amount of food they eat through calories counting. About 1 in 8 adult American knows how to count calories. This increasingly popular method of losing weight is even endorsed by the First Lady Michelle Obama.


But what happens when counting calories reaches obsessive levels, nearly equal to starving? The objective of the current study was to figure out the effects of diet control and exercise. The results showed different outcomes which were then compared.

Professor Doucet stated, “Although dieting alone produces more weight loss than exercise alone, this study confirms that compared with depletions by exercise alone, acute caloric restriction results in rapid changes in appetite that result in compensatory eating, which may initially dissuade potential success in weight-loss efforts.”

Eric Doucet, Ph.D. was the lead author of the study, who is an expert in obesity and also a professor at the University of Ottawa. The study employed the model to observe the impact difference on appetite standards such as olfactory perceptions e.g., taste, smell etc., hunger controlling hormones e.g., lepti n, ghrelin etc., ad libitum i.e., free eating, and food reward behavior. The study was performed on 10 males belonging to the age groups 18 years to 40 years old, with the mean age being 23.7 years old. The pilot trial was carried out at the Behavioral and Metabolic Research Unit at the University of Ottawa in Canada from 12th March, 2010, to 1st December, 2011. The male subjects were recruited on voluntarily basis and filtered for any illnesses which may alter the outcomes of the research. For example, smokers, diabetics and overweight individuals were excluded from the study.

The participants were first subjected to the same control conditions and were then divided into two groups, selected by a computer-generated algorithm and subjected to the different conditions for a four-day period. One of the groups was first subjected to a limited diet followed by aerobic exercises. Meanwhile, the other group was first subjected to aerobic exercises and then the calories in their diet were restricted. The interval between exposure to restricted diet and aerobic exercise was set at two weeks which gave the subjects ample time to regroup. Following all the research conditions, the anthropometric measurements and blood samples of the subjects were readily taken, which was followed by a questionnaire.

Caloric content or energy was depleted by 25% in the diet provided to the subjects and only contained 500–700 kcal per day. The food menu used was validated from the research laboratory and contained isocaloric foods i.e., foods with same caloric content. The diet included of a standard breakfast and lunch, but the dinner comprised of a buffet containing self-selected favorite food items e.g., fruits, vegetables and even snacks (chips, chocolate and candy). In the same way, the volunteers were subjected to aerobic exercises to cut down their calorie count by 25%. The participants were told to do brisk walking for one hour on a treadmill. The researchers used the aerobic capacity test, which measures the maximum levels of oxygen consumed during the session to determine the number of calories burned.

As was theorized at the start of the study, considerable differences were observed in body weight loss as a result of separate conditions. The results showed odor response to food increased after consuming a restricted diet when compared to responses after exercise. After going through a restricted diet, the subjects showed greater inclination to hunger, desire to over-indulge and cravings for favorite foods. Excessive restriction of dietary calories was found to be a greater problem for individuals wishing to slim down rather than regular cardio exercises. The research advises following a program which cuts down weight with the aid of aerobic exercises and without having to starve oneself.

Surprisingly, the blood tests showed the plasma levels of hormones leptin or total ghrelin that did not vary in both experimental conditions. Leptin and ghrelin are very important hormones of the human body and are basically involved in regulation of energy balance. Leptin is responsible for curbing hunger while ghrelin is responsible for setting off hunger. Surveillance on levels of both the hormones is very important since they are found to be involved in development of obesity. A drawback of study is the examination of only fasting leptin and ghrelin levels, which cannot accurately define the effects of the conditions on the entire metabolism. Since both hormones have a far greater role in the fate of the body mass than perceived in the current study, the next phase would be to observe the effects of various diet and exercise regimes on the body metabolism.

Although the study provided valuable data on weight loss regimes; it did have one very noticeable limitation i.e., the small sample size comprised of relatively young individuals who were already healthy. Such a small and constricted study sample cannot be used as an example for the entire population.

One very glaring limitation of the research was the exclusion of the female population, which is equally affected by the obesity prevalence in the U.S. According to the U.S. NIH, about 64% of women were obese or overweight in 2010. Compared to men, women are also known to have different hormonal effects when they go without food and exercise. Nutrition experts recommend using techniques such as calorie counting for women to maintain a healthy weight. Research has shown weight loss interventions such as calorie counting and food monitoring as an effective tool to shed extra pounds for women over a period of 12 months.

Similarly, the researchers based some of their conclusions on the basis of heightened sense of smell. Although they used the ‘Sniffin’ sticks’, which is a relatively new test used to detect chemosensory performance of the nasal cavity, the test cannot accurately determine if the sense of smell is heightened in everyone after fasting. The device has a pen-like odor dispensing shape and tests three olfactory functions, which are the odor threshold by using n-butanol, odor discrimination and odor identification.

Professor Doucet stated, “To our knowledge, this is the first study to show a link between diet-induced depletion changes in nasal chemosensory performance and ad libitum EI, highlighting the need to further study the dynamic role of olfaction in appetite and body weight regulation.”

Likewise, the study was based on short term effects of diet and exercise, and long-term energy depletion through diet which may give different results. Healthcare experts advise using calorie counting techniques in moderation with other techniques for a long time. The current study based their result on a very short term analysis and with the current obesity epidemic in America, more data is needed to come up with a concrete conclusion.