Do Calories Really Matter?

Energy Balance Background 

It is important to remember that the basis of weight control is energy in compared to energy out. Metabolism is “all the chemical reactions that occur in the body” and energy metabolism are all these chemical reactions involved in the “breakdown, synthesis, and transformation of the energy-yielding nutrients-glucose, amino acids, and fatty acids-that enable the body to store and use energy” (McGuire & Beerman, 2013, p. 271). The energy source of the cell is not the calorie, but ATP; therefore not all calories are created equal. A calorie from a nutrient dense source is able to “fuel” a body at a higher, denser level than empty calories. Metabolism involves a variety of pathways and enzymes that work together to create energy from a variety of components (glucose, glycogen, fatty acids, amino acids, and more) from a variety of tissues . The body can get energy (ATP) from a variety of pathways, some of which are more optimal than others. So how does this affect weight loss?

To maintain weight one must be in a state of energy balance where energy in equals energy out. Weight loss comes negative energy balance where energy intake is less than energy out. As stated previously, the energy source of the cell is ATP, not calories. Energy balance is extremely individualized with metabolic rate being affected by: genetics, gender, age, weight, height, body fat percentage, diet, body temperature, external temperature, endocrine function, and exercise (Greenfield, 2014, p. 279). Diet is only part of the metabolic process, but is so important because it is the main source of energy in. The rest of energy balance components are more involved with energy utilization, storage, and use. In order to maintain weight loss and control body weight a diet or hopefully lifestyle needs to be sustainable. A negative energy diet with too much energy out can result in amino acid breakdown (lean body tissue), tiredness, hormonal changes, and overall a state of starvation which is not healthy or sustainable. Finding nutrient dense foods that minimize hunger by giving people many nutrients and a feeling of satiety can help optimize healthy eating.

There are ways to increase metabolism or the energy utilized in the body including: diet, exercise, external temperature, hormonal changes, and genetics. Eating foods can affect metabolism, like good protein dense sources or fiber rich foods, which have a higher thermic effect of food (TEF) and utilize more energy of the body during the digestion process (McGuire & Beerman, 2013, p. 334). Eating nutrient dense sources will help optimize functioning during periods of negative energy balance as well. Exercise increases metabolism by increasing internal temperature which increases basal metabolic rate (BMR) during exercise and increases lean muscle mass which burns more calories than body fat, even when you aren’t exercising (Greenfield, 2014, p. 279). External temperature can increase metabolism because in cold or hot conditions the body has to utilize energy to maintain the body temperature, seen when a person sweats or shivers in extreme conditions.

Hormonal Effects

There are a number of important hormones that affect energy intake through promotion or reduction in the feelings of hunger and satiety. The brain controls these feeling by receiving signals from hormonal response and nutrient response in the body. Levels of circulating lipids, proteins, and carbohydrates promote feelings of fullness through release of neurotransmitters to the brain’s hunger and satiety center, the hypothalamus. Ghrelin is an important hormone because its release in response to an empty stomach stimulate a feeling of hunger (McGuire & Beerman, 2013, p. 325). Ghrelin is a GI hormone, meaning that its release is controlled by the direct effect of food on the part of the GI tract. Leptin is another important hormone in body weight regulation, its release decreases the feeling of hunger. Impaired leptin signals are directly correlated with weight gain (Orr & Daly, 2005). Foods that are high-volume can help decrease release of ghrelin and increase feeling of satiety through release of leptin.

Fluctuations in the hormones of insulin and glucagon are directly related to obesity. Eating a diet high in sugar is linked to obesity because high sugar consumption results in periods of hyperglycemia and then hypoglycemia stimulating release of insulin and glucagon. Prolonged diets high in sugar can result in pancreatic dysfunction or inability to release the appropriate amounts of insulin, known as diabetes. Eating a lower or controlled carbohydrate diet is also linked to better hormonal control of insulin as well as ghrelin and leptin (Orr & Davy, 2005). Sugar is also linked to hormonal release of serotonin, which makes us feel good, therefore making sugar addicting and directly related to stressful eating described in lifestyle factors on energy balance (Shullman, 2011).

Lifestyle and Genetic Factors

There are many lifestyle and genetic factors that contribute to weight loss and obesity including: stress, food choices, gender, and inherited make-up. People tend to have food cravings during certain times in the day and in response to stressful situations; with women tending to experience food cravings more frequently than men in part due to hormonal fluctuations in the relation to the menstrual cycle and pregnancy (McGuire & Beerman, 2013, p. 330). Prevention and management of stressful situations through diet, exercise. and proper sleep can help with “stressful eating” and hormonal control. Exercise is important in weight loss through benefits including: increasing energy used, increasing metabolism, helps manage stress, addition of lean body tissue, and better sleep (also linked to reduction in stressful eating). Eating high-volume, low-energy, and nutrient dense foods, like fruits and vegetables, are optimal for weight loss because they are high in water and/or fiber while providing nutrients at high levels (McGuire & Beerman, 2013, p. 328). This results in feelings of satiety, good energy levels during energy restricted periods, and helps prevent use of body amino-acids for energy.

Genetic factors do influence obesity risk factors and until recently it was thought that we can’t change our genetic make-up; however new research is coming out supporting change in genetic makeup that can be positively promoted through proper diet, exercise, and other lifestyle choices. Researchers have seen that conditions in the womb “can prompt epigenetic chances that later influence a person’s body weight” and scientists “estimate that at least 50% of our risk for becoming overweight or obese is determined by genetics or epigenetics” (McGuire & Beerman, 2013, p. 345). There are genetic codes that increase risk of obesity and diabetes as well as genetic links to deficiencies or resistance to hormones, like leptin. Genetics do play a role in weight regulation, but as the science of epigenetics suggests the lifestyle choices we make every day can change our genetic makeup.

There is a lot more that goes into weight loss than counting calories. In order to lose body fat, energy out needs to be greater energy in. There are many ways to enhance energy used like: exercise, increasing metabolism, and even eating certain nutrients. If a diet is not filling and sustainable the lifestyle won’t be optimal. Hormonal response to hunger, satiety, and other environmental variables like stress also affect optimizing energy balance. Proper food choices, exercise, and other lifestyle choices along with genetics are all involved with metabolism. A good way to promote positive energy choices is by eating high volume, low energy, and highly nutritious foods. Our lifestyle choices affect not only our holistic health, but the genetic makeup of our children.


Greenfield, Ben. (2014). Beyond training: Mastering endurance, health, & life. Las Vegas: Victory Belt Publishing, Inc.

Inui, A., Asakawa, A., Bowers, C.Y., Mantovani, G., Laviano, A., Meguid M.M., & Fujimiya, M. (2004). Ghrelin, appetite, and gastric motility: The emerging role of the stomach as an endocrine organ. Federation of American Societies for Experimental Biology Journal 18, 439-456. Retrieved from,%20appetite,%20and%20gastric%20motility.pdf

McGuire, M. & Beerman, K.A. (2013). Nutritional sciences: From fundamentals to food. Belmont, CA: Wadsworth.

Orr, J., & Davy, B. (2005). Dietary influences on peripheral hormones regulating energy intake: Potential applications for weight management. Journal of the American Dietetic Association 105, 1115-1124. doi: 10.1016/j.jada.2005.04.005

Shulman, J. (2011). Cast out those cravings: manage your blood sugar levels. Alive: Canada’s Natural Health & Wellness Magazine 339, 37

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