Not just the “what” but also the “how much” you eat matters

In the age of intermittent fasting, plant-based diets and Whole30, fad diets boast about their long-term health benefits, while simultaneously overcomplicating what it means to have a healthy lifestyle. The reality is, it’s hard to precisely measure the accuracy of these claims, let alone, keep even the most devout ketotarian from reaching for that pasta or chocolate cake long enough to be able to quantify long-term effects on chronic disease and lifespan. Fortunately, we likely don’t need some restrictive diet to experience healthful benefits and many of these can be achieved through maintaining a simple energy balance, where energy in equals energy out. In other words, energy balance is achieved when energy consumed through foods and beverages (energy in) is equal to the energy burned through basal metabolic functions and physical activity (energy out). Extensive literature has shown energy balance is important for overall health and disease prevention, however there is still a lot more to understand about this in relation to chronic disease risk factors. The Nutrition and Physical Activity Assessment (NPAAS) Group from the Public Health Sciences Division at Fred Hutch- which includes Drs. Ross Prentice, Johanna Lampe and Marian Neuhouser- is substantially interested in understanding energy intake through diet and its relationship to mortality and other clinical outcomes. In their recent study published in The American Journal of Clinical Nutrition, Prentice et al. investigated the total energy expenditure (TEE) for a cohort of postmenopausal women and asked how it related to mortality risk over a 19-year period. The NPAAS group explained that the motivation for this study was to “provide a fresh look at the association between energy intake in relation to chronic disease risk, including cancer. Energy intake is poorly measured by self-reported diet and accordingly has been substantially overlooked in nutritional epidemiology research.” In this recently published work, the researchers uncovered an interesting age-dependent association between TEE and all-cause mortality that may prompt revision to the saying “you are what you eat”, as this research shows that how much you eat, might be just as important.

To evaluate how a person’s energy intake and expenditure might relate to mortality, the researchers measured total energy expenditure (TEE) as “the number of calories a person expends (or uses). It is the energy used, in a resting state, to support basic metabolic processes, plus that used during physical activity,” the research team stated. For a person in ‘energy balance’, the amount of energy they expend (TEE) will be equal to the amount of energy they take in through consuming food and beverages. As you might expect, “long term energy intake in excess of TEE can lead to overweight and obesity, which are linked to over 15 types of cancer,” the NPAAS team explained. To precisely and accurately measure TEE, the researchers used a chemical tool called doubly labeled water (DLW). This water is like “normal everyday water labeled with two stable isotopes: deuterium and oxygen18,” the researchers noted. The “heavy” oxygen18 and hydrogen-mimic deuterium isotopes allowed the researchers to trace these molecules through urine samples, which take about two weeks to be completely excreted. “The excreted isotope concentrations in the urine are measured by mass spectrometry and the results give a reliable estimate of carbon dioxide production and water (H2O or in this case D2O18) excretion over the prior two weeks. Since CO2 and H2O are the end products of metabolism, the results give a reliable, quantitative measure of the number of kcals used (e.g., energy expenditure) over the two-week period. In weight stable people, energy expenditure is approximately equivalent to energy intake. This is why we can use this doubly labeled water test to determine the number of kcals a person ingests over a short time frame,” explained the NPAAS group.

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