Challenges Interpreting Inpatient and Outpatient Human Nutrition Studies

From dearth to excess: the rise of obesity in an ultra-processed food system

More people now have obesity than suffer from starvation thanks to our modern food system. Agriculture was transformed over the 20th century by a variety of technological advancements that relied heavily on fossil fuels. In the United States, government policies and economic incentives led to surplus production of cheap inputs to processed food industries that produced a wide variety of heavily marketed, convenient, rewarding, timesaving, and relatively inexpensive ultra-processed foods. The energy available in the food supply increased by much more than the population needs, albeit with large inequities in nutrition security. While most of the rise in per capita food availability during the late 20th and early 21st centuries in the United States resulted in increased food waste, a variety of mechanisms have been proposed by which changes in the increasingly ultra-processed food environment resulted in excess energy intake disproportionately in people genetically susceptible to obesity. As populations continue to grow, substantial investments in coordinated nutrition and agricultural research are needed to transform our current food system to one that relies less on fossil fuels, preserves biodiversity, ensures environmental health, and provides equitable access to affordable, safe and nutritious food that reduces the prevalence of chronic diet-related diseases like obesity. This article is part of a discussion meeting issue 'Causes of obesity: theories, conjectures and evidence (Part I)'.

French-fried potato consumption and energy balance: a randomized controlled trial

BACKGROUND

Epidemiologic observations suggest increased potato consumption correlates with weight gain, adiposity, and diabetes risk, whereas nut consumption is associated with weight control and metabolic health. Randomized controlled trial (RCT) data indicate humans respond to changes in energy intake in single dietary components and compensate for extra energy consumed.

OBJECTIVES

We completed an RCT testing whether increased daily potato consumption influences energy balance [specifically, fat mass (FM)] compared with calorie-matched almond consumption.

METHODS

A 30-d RCT of 180 adults prescribed calorie-matched (300 kcal/d, n = 60 participants/group) than consumed 1 of the following: 1) almonds (almond group), 2) French fries (potato group), or 3) French fries with herb/spices mix (potato + herb/spices group). Baseline and 30-d FM were measured by DXA (primary outcome), with secondary outcomes including body weight and carbohydrate metabolism markers [glycated hemoglobin (HbA1c), fasting blood glucose and insulin, HOMA-IR)]. A subset of 5 participants/group participated in a postprandial meal-based tolerance test.

RESULTS

A total of 180 participants were randomly assigned [gender: 67.8% female; mean ± SD age: 30.4 ± 8.7 y; BMI (in kg/m2): 26.1 ± 4.2; and weight: 75.6 ± 15.4 kg], with 12 dropouts and 3 terminations. No significantly different FM changes were observed between almond and potato consumption [combined ± herb/spices; mean ± SE almond: 230.87 ± 114.01 g; potato: 123.73 ± 86.09 g; P = 0.443], fasting glucose (P = 0.985), insulin (P = 0.082), HOMA-IR (P = 0.080), or HbA1c (P = 0.269). Body weight change was not significantly different in the potato groups combined compared with the almond group (P = 0.116), but was significantly different among the 3 groups (P = 0.014; almond: 0.49 ± 0.20 kg; potato: -0.24 ± 0.20 kg; potato + herb/spices: 0.47 ± 0.21 kg). In meal tests, significantly lower post-prandial glucose and insulin responses to almonds compared with potatoes were observed (P = 0.046, P = 0.006, respectively), with potato + herb/spices having intermediate effects.

CONCLUSION

There were no significant differences in FM or in glucoregulatory biomarkers after 30 d of potato consumption compared with almonds. Results do not support a causal relation between increased French fried potato consumption and the negative health outcomes studied. This trial was registered at clinicaltrials.gov as NCT03518515.