On Energy Balance and Weight Control— Is a Calorie a Calorie?

The Energy Balance Key

Energy balance is key to maintaining a healthy body weight and composition. Energy balance can be achieved with a wide variety of dietary patterns, and various tactics, respectively. No convincing evidence exists that the first law of thermodynamics has been subverted (i.e., a calorie is still a calorie), as sometimes argued by some weight loss advocates (e.g., keto/ultra-low carb). To the contrary, ¹ a number of metabolic chamber studies such as a recent study from Hall and colleagues ² at the National Institutes of Health suggest that a ketogenic state suppresses appetite to ultimately reduce energy intake. ³ A higher fraction of initial weight loss (e.g., vs. an ultra-low fat approach) associated with a ketogenic diet is water fraction loss due to carbohydrate depletion (in vivo carbohydrate requires far more water per calorie than fat to solubilize in tissues).

In addition to keto, there are multiple tactics commonly employed in the hopes of reducing non-essential calorie intake to a level that results in health benefits. These are most often due to desire to lose weight, often with an actual target of inducing varying degrees of pre or full type 2 diabetes (T2D) remission. But other targets of calorie balance include longevity, cancer risk reduction and cardiovascular (CVD) risk reduction. ⁴ Notably, CVD reduction ideally includes nutritional attention beyond calorie balance to include, for instance, sodium/potassium, saturated fat (and for hyper-absorbers or those with established CVD or T2D, cholesterol), which is beyond the scope of this article.

Calorie Density Approach

Let’s turn to relevant ways those attempting to control calorie intake try to achieve and maintain a balance consistent with better body composition and health. From author Rifai’s perspective after spending almost 2 decades and over 20,000 clinical direct patient care hours leading multidisciplinary care metabolic health and weight management programs, the leading, albeit certainly not only, factor associated with ad libitum calorie intake in a free, modern Western Society is calorie density (CD). Also, commonly known as “Volumetrics,” this approach considers the major impact the weight/volume of solid to semi solid food plays in satiety (i.e., a sense of no longer being hungry). ⁵

CD, the calories per gram (or pound) of a solid to semi-solid food (most beverage calories are not nearly as satiating, ostensibly, due to their non-viscous liquid nature, and therefore not appropriate to consider in calorie density equations) runs from less than 100 to 4000 calories per pound or 0.2 calories per gram up to pure fat at 9 calories per gram (i.e., from low starch vegetables to oils). Currently, free living humans in Western societies eat on average around 2.5 to 3.0 lbs of produced food (i.e., from minimally processed to highly refined solid to semi-solid foods, not including low/non-satiating beverage calories), depending on individual characteristics and foods chosen. ⁶ Tactics to reduce the total food volume (i.e., food weight) one eats (“portion control”) is more challenging than maintaining (or even increasing) total volume of food intake where intake is adjusted towards those with “less calories per bite” (i.e., lower CD); in other words, “volumizing” foods. It is an approach recognized by the CDC as well as nutrition researchers and experts. ^5,7 Since whole fruits and vegetables address reducing calorie density substantially and have consistently documented health benefits, they and other water rich plants (esp. cooked whole grains and legumes which are “bulked up” with added cooked-in water) would be a high priority in terms of calorie density-based eating. Calorie density could also be applied a wide spectrum of animal-based foods from yogurts and egg whites (low calorie density), which would need less portion control concern versus fatty meats and extracted fats like butter and tallow (very high calorie density), which would require much higher levels of portion and frequency control.

Satiating Nutrients

There is also data to suggest that in order to minimize hunger, calorie reduction attempts should not include dramatic drops in protein intake, though the source of protein is a major question in terms of digestion kinetics. ⁸ It is worth noting briefly that in light of the importance of what humans eat for protein and energy balance having impacts beyond calories and amino acid spectrum vis-à-vis personal health, but also environmental ramifications, ⁹ legumes (lentils, beans and peas) can be considered some of the highest overall quality sources for protein when seeking satiation with less calories. ¹⁰ Increasing fiber as well has been part of many calorie balance investigations with suspected satiety enhancing effects. ¹¹ And while the effects on satiety for naturally occurring, intact fiber, is less clear in published data, the author’s clinical experience is consistent with higher intact fiber intake resulting in easier management of reduced calorie intake and calorie balance, and with it successful, healthful, weight reduction. In light of the many more clearly established health benefits of high fiber intake, advising higher fiber intake as an adjunct to calorie management is one that has little risk of harm and substantial upside benefits versus the low average American intake of fiber rich, minimally and unrefined foods. ¹²

Challenges to Calorie Reduction

A major challenge for most in trying to achieve energy balance in favor of sustainable reduced calorie intake is the omnipresence of calorie rich, refined and highly processed (acronym: CRRAHP), hyperpalatable food-like products and beverage calories which is entirely out of sync with food/calorie availability throughout most of human history.

With such hyper-palatability taking advantage of inherent human tendencies to seek calorie rich sources of food through most of human evolution, we are challenged with omnipresent, tempting CRRAHP foods and non-satiating (mostly sugary, but also creamed and alcohol) beverage calories, making energy balance in favor of healthy major effort, even for the motivated. We are also challenged by sensory specific satiety. ¹³ A picture speaks a thousand words. And we can all picture innumerable Americans in restaurants or during holidays (possibly often us) saying: “I’m so full, I can’t eat another bite.” This, then, is often followed by an “unexpected appearance out of nowhere” of a spectrum of desserts on a “dessert tray.” Then, despite our previous exhortation we (not so) oddly can suddenly “eat another bite,” of a “yet to be satiated” flavor…of dessert, that is.

In summary, the impressive evidence presented that food weight matters to satiety, combined with an innumerable array of CRRAHP foods and calorie-based, low-satiation, beverages likely drive much of modern society’s challenge with healthy calorie balance. Yes, “we are what we eat” (and drink), but we largely “eat what surrounds us.”

Intake Timing and Other Factors

Other factors and tactics that have been applied to control calorie intake are numerous, but some that have reached common public utilization include intermittent fasting methods such as time restricted feeding, alternate day fasting, 5:2 fasting as well as medical formula or commercial meal replacements. ¹⁴ Let there be no mistake though, there is no “secret” to calorie balance. These approaches, if weight loss is a result, are still tactics to control calories, to which we cannot “hack” our way around. Of course, the issue of calorie control is of such urgency that there are numerous FDA approved weight loss drugs ^15,16 for the putative effect of reduced calorie intake via reduced appetite.

Dietary Patterns Are Not Exclusive of Calorie Control Tactics

Beyond calorie density, fiber and attention to protein adequacy, the “how” one can moderate calorie intake can be in the form of many variations of “what.” For example, one could apply time restricted feeding to a plant predominant dietary pattern (e.g., Flexitarian, Vegetarian, Mediterranean) or even the standard American diet. In my clinical experience, there are advantages to incorporating some intuitive eating principles. ^17,18 Whatever tactic(s) used to maintain calorie target to achieve or maintain body leanness, a lifestyle strategy becomes a long-term strategy, lest risk “yo-yo dieting” (though what foods are eaten in yo-yoing seem more important than yo-yoing itself). ¹⁹ Lastly, any dogma about “one best way” to achieve lasting calorie balance, which often translate too readily into pop culture memes, is not consistent with the state of current evidence. There is, for instance, no “metabolic magic,” to intermittent fasting (IF). ²⁰ While IF may be a helpful for those who prefer it to simple continuous calorie reduction, any good calorie control tactic must be coupled with a dietary pattern that is healthful in many other important regards including but not limited to, sodium, intact fiber and saturated fat.

In terms of calorie balance for long term weight maintenance of weight loss, 2 notable sources are the National Weight Control Registry ²¹ —a database of thousands of volunteer subjects who have maintained weight loss long term—and the Look AHEAD trial. ²² Look AHEAD is the longest, largest RCT of intensive lifestyle intervention-based weight reduction ever performed (10 years). What do we know from these 2 resources? Modification of food intake and increased physical activity are paramount.

In summary, calorie balance in favor of health is a challenge in a modern environment awash in CRRAHP foods and beverage calories, especially as the first law of thermodynamics still applies in that, ultimately, a calorie is a calorie. Nevertheless, many methods of eating can be combined with healthful food choices and reduced beverage calories, typically in the direction of lower calorie density and higher nutrient density of foods, with the highest priorities being increasing whole fruit and vegetable intake as well as cooked legumes and (especially intact) whole grains, as well as other high intrinsic water content foods. This should be combined with modification of one's common environments (e.g., home, work, car) to keep healthy foods close and CRRAHP foods and beverage calories at as much of a distance as reasonably possible to minimize battles against temptation.