不吃早餐会让你变胖？随机对照试验发现……

　　问：不吃早餐会导致体重增加么？

　　在我小一些的时候，妈妈说，如果不吃早餐，我的新陈代谢就会被“训练”得减慢下来，从而导致体重增加和相关的健康问题。可我比较喜欢起床后的一两个小时内只喝茶吃点心。妈妈的理论到底对不对？

　　答：数十年来，食品行业一直在宣传这种说法，以便推销他们的早餐麦片。但是，严谨的科学研究并未发现有什么证据可以证明这种理论。

　　丰盛的早餐有益健康这种说法可以追溯到20世纪20年代，当时有个名叫爱德华·伯内斯（Edward Bernays）的公关大佬领导了一项全国性的媒体宣传活动，鼓励人们早餐吃培根和鸡蛋。而当时，伯内斯先生的一个客户正是销售培根等猪肉制品的比纳肉类加工公司（Beech-Nut Packing Company）。

　　在随后的几十年里，数十项观察性研究报告指出，吃早餐的人往往更瘦。尽管这些研究并不能证明其中的因果关系，但很多健康专家和食品公司都宣称他们已经证实，吃早餐可以防止体重增加。

　　然而，在将人随机分为吃早餐组和不吃早餐组的研究中，并没有得出此类结论。

　　2016年3月，英国巴斯大学和诺丁汉大学发表在《美国临床营养杂志》的随机对照试验发现，在六周期间，分配入吃早餐组与不吃早餐组的参与者在“体重和绝大多数健康预后方面”没有什么差异。

　　该研究的作者、英国巴斯大学营养和代谢学副教授詹姆斯·贝茨（James Betts）说：“吃不吃早餐本身并不会影响你的体重。”

　　贝茨博士说，与随机试验不同，关于吃早餐的观察性研究有可能会造成误导。例如，它们显示，吃早餐的人往往也遵循与身体健康相关的其他行为。与不吃早餐的人相比，吃早餐者一般较少抽烟喝酒，糖的摄入量更少，较多地摄入纤维性食物，锻炼也更加积极。

　　“我们从观察性研究得知的只是吃早餐的人更瘦。”他说。“但是，在其中发挥因果作用的很可能是其他的因素。”

Am J Clin Nutr. 2016 Mar;103(3):747-56.

The causal role of breakfast in energy balance and health: a randomized controlled trial in obese adults.

Chowdhury EA, Richardson JD, Holman GD, Tsintzas K, Thompson D, Betts JA.

Departments of Health and Biology and Biochemistry, University of Bath, Bath, United Kingdom; School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, United Kingdom.

BACKGROUND: The causal nature of associations between breakfast and health remain unclear in obese individuals.

OBJECTIVE: We sought to conduct a randomized controlled trial to examine causal links between breakfast habits and components of energy balance in free-living obese humans.

DESIGN: The Bath Breakfast Project is a randomized controlled trial with repeated measures at baseline and follow-up among a cohort in South West England aged 21-60 y with dual-energy X-ray absorptiometry-derived fat mass indexes of ≥13 kg/m(2) for women (n = 15) and ≥9 kg/m(2) for men (n = 8). Components of energy balance (resting metabolic rate, physical activity thermogenesis, diet-induced thermogenesis, and energy intake) were measured under free-living conditions with random allocation to daily breakfast (≥700 kcal before 1100) or extended fasting (0 kcal until 1200) for 6 wk, with baseline and follow-up measures of health markers (e.g., hematology/adipose biopsies).

RESULTS: Breakfast resulted in greater physical activity thermogenesis during the morning than when fasting during that period (difference: 188 kcal/d; 95% CI: 40, 335) but without any consistent effect on 24-h physical activity thermogenesis (difference: 272 kcal/d; 95% CI: -254, 798). Energy intake was not significantly greater with breakfast than fasting (difference: 338 kcal/d; 95% CI: -313, 988). Body mass increased across both groups over time but with no treatment effects on body composition or any change in resting metabolic rate (stable within 8 kcal/d). Metabolic/cardiovascular health also did not respond to treatments, except for a reduced insulinemic response to an oral-glucose-tolerance test over time with daily breakfast relative to an increase with daily fasting (P = 0.05).

CONCLUSIONS: In obese adults, daily breakfast leads to greater physical activity during the morning, whereas morning fasting results in partial dietary compensation (i.e., greater energy intake) later in the day. There were no differences between groups in weight change and most health outcomes, but insulin sensitivity increased with breakfast relative to fasting.

This trial was registered at www.isrctn.org as ISRCTN31521726.

KEYWORDS: appetite regulation; breakfast; energy balance; energy intake; fasting; metabolism; obesity; physical activity

PMID: 26864365

PMCID: PMC4763497

DOI: 10.3945/ajcn.115.122044