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How to optimize your body clock to lose weight
Scientists have worked out exactly what you should be doing and when for effective weight loss. Here’s our round-the-clock guide
If you’re really serious about losing weight, you’ll be working out while the rest of the world is pouring their first cup of Earl Grey. According to a new study of more than 5,000 people from Franklin Pierce University in New Hampshire in the USA, the best time to exercise is between the hours of 7am and 9am.
Researchers found that people who did 150 minutes of pre-work exercise a week were six pounds lighter and had a lower BMI than those who exercised later in the day. They were also less likely to have unhealthy diets and consumed fewer calories than those who exercised in mid morning or later.
“Our findings propose that the diurnal (daily) pattern of moderate to vigorous physical activity could be another important dimension to describe the complexity of human movement,” says study author Dr Tongyu Ma.
Is it possible to continue this calorie-burning fest throughout the day? Here’s our round-the-clock guide
7am: Time to wake up
While it’s true that some people are naturally night owls, the 21st-century rat-race is geared to the morning larks.
Be consistent with your wake up times
Stay consistent with your wake-up times in order to remain healthy, says Professor Whitmore CREDIT: Alamy
“The idea now is that every organ, and possibly every cell has its own clock, and these are synchronized by a clock in the brain, which itself is set by photo-receptors in the eye that respond to light,” says Professor David Whitmore, who specializes in chronobiology (the way that our biology is affected by time) at University College London.
Ideally, you’ll be consistent with your wake-up times. “If you keep a regular sleep-wake cycle, regular meal times and regular light-exposure times, that keeps the whole body-clock on time, which in turn keeps everything else on time,” says Dr Guy Meadows, sleep expert and founder of Sleep School.
7.20am: Get your running shoes on
According to Dr Ma, cardiovascular exercise is likely to be key for those who work out in the mornings. “Exercise can burn fat and glucose,” Dr Ma says.
Exercising before breakfast will more likely help burn fat
“After an overnight fast, the glucose stored in our body is low. Therefore, when we exercise our muscles are likely to burn more fat. I would recommend 40 minutes of aerobic exercise before breakfast, such as running or biking.”
10am: Eat breakfast
Various studies have shown the benefits of intermittent fasting for weight loss and scientists from King’s College London recommend eating within a 10-hour window. 10am offers the chance to fast slightly later in the morning, so you can finish eating before 8pm in the evening and give your body time to digest before bed. A study from the University of Surrey found that pushing your eating time 1.5 hours later results in you eating fewer calories.
Start your day with a form of protein such as eggs
Starting your day with a form of protein such as eggs can help stave off hunger later in the day.
“There’s evidence to show that eating in line with your body clock will improve your metabolic health, inflammation and weight,” says Dr Sarah Berry, a leading nutritional scientist.
Focus on starting your day with protein: eggs or salmon. Studies from Japan have found that people are better at metabolizing and building muscle from protein when it is consumed in the morning compared to when it is consumed in the evening.
12pm: Finish your last cup of coffee
While one unit of alcohol takes an hour for the body to break down, it takes up to six hours for it to clear the caffeine from a single shot of espresso from your system. “At minimum, you need to leave at least a six-hour break between drinking coffee and going to sleep,” advises Dr Meadows. “Drink two or three cups a day if you like, but ideally stop at noon.”
When is the best time to exercise, drink coffee and have dinner?
Researchers found that people who did 150 minutes of pre-work exercise were six pounds lighter
This is important because a lack of good quality sleep can lead to increased consumption. “When we’re sleep-deprived, our bodies raise levels of [the hormones] ghrelin, and lowers leptin, meaning we’re hungrier and find it harder to feel satiated,” says hormone expert Emma Bardwell. These hormones are vital in regulating appetite. Ghrelin tells the brain that you’re hungry, while leptin tells you that you’re full and can stop eating. That means if you’re sleep-deprived you’re likely to eat more.
2pm: Eat some carbs now
This is the meal where you should get most of your carbs, says Ulrike Kuehl, head of nutrition at the metabolism-tracking app, Lumen. “Consuming carbs midday will be important to give you some fuel to get you through the rest of the day,” she says.
“It makes sense for most people if you look at the average metabolic flexibility to have more carbs in the middle of the day, that’s when people tend to be more sensitive to insulin and so better at processing them.” All this is even more important to give you energy to exercise after work.
3.42pm (or whenever you feel like it): Give yourself a short break to day-dream or do nothing
“One of the big problems these days is that the only time we take to pause is when we go to bed,” says Dr Meadows. “That’s when your mind races because your Default Mode Network, the part of your brain responsible for mental chatter, hasn’t had the chance to catch up on the day. Factoring in simple breaks to just do nothing is essential to sleep better later.”
We should get up from our desks every hour and walk for two minutes, according to the British Medical Journal
In 2015, a group of scientists from around the world published guidelines in the British Medical Journal, advising that we should get up from our desks every hour and walk for two minutes. Doing so cuts the risk of premature death by 33 per cent by burning calories and keeping the body active.
5pm: Grab some weights (or your yoga pants)
A 2019 study from the Scripps Research Institute in California found that between 4pm and 6pm your core body temperature is at its highest and your muscles and joints are most warmed up. Now is the time when you’ll get the most out of strength and movement exercises. Exercises like this are good for building muscle which, in turn, is vital for burning fat. This is because muscle tissue requires more calories to maintain than fat tissue.
Now is the time when you’ll get the most out of strength and movement exercises
Early evening is when you’ll get the most out of strength and movement .
“The more muscle you have, the more calories you will burn,” says three-time Olympic speed skater and top personal trainer, Sarah Lindsay. “Of course, cardio and general activity are great for you in all sorts of ways, but it needs to be combined with getting stronger.”
A 2018 review of 23 different studies about exercise timings found that people who exercised in the evening fell asleep faster and spent more time in deep sleep. Be wary of exercising too close to your bedtime or exercising too intensely late into the night though: the review found that intense exercise in the hours before bed delayed sleep onset by an hour.
6pm: Finish dinner
“The most effective thing people can do for their weight loss is to eat a couple of hours earlier in the evening than they might think - I’d say three or four hours before bed,” says Kuehl.
“If you eat late at night, it increases blood glucose and insulin, which negatively impacts sleep. The cells of your metabolism need time to rest and regenerate so if those cells are active your body has trained itself not to shut down until they do. If you don’t sleep well, you’re more likely to gain weight.”
8pm: Skip the glass of wine while you’re watching TV
It might be tempting to crash on the sofa with a glass of wine, but it’s generally unwise. “The body detects alcohol and sees it as a toxin, so it focuses all its resources on detoxifying that alcohol,” explains Inside Performance sports scientist Nigel Stockill. All the processes by which the body would normally start to get you ready to sleep, such as slowing down the heart rhythm, get neglected until the body has detoxified the alcohol.
“The body detects alcohol and sees it as a toxin", says sports scientist Nigel Stockill
“As little as one unit of alcohol in your system at bedtime can delay the onset of restorative sleep by about an hour. Have two large glasses of wine (approximately 6 units) late in the evening and sleep for six hours and you may not get any restorative sleep, and therefore won’t recover overnight. And you’ll also crave carbs the next day.”
10pm: Get to bed
Ideally you’ll have been slowing down, closing your curtains, and switching off your smartphone before this point, but aim to get about eight hours of sleep to help lose weight. A 2022 study from the University of Chicago Medical Centre found that going to bed 75 minutes earlier than you would otherwise helps you consume 270 fewer calories (the equivalent of three biscuits).
In 2016, one study found that levels of a chemical called 2-arachidonoylglycerol (2-AG), which increases the amount of pleasure we derive from eating, rose by a third when volunteers were sleep-deprived. In short: you’ll want to eat more. So do yourself a favour and off you go to bed.
注释：
Earl Grey: n
表示"伯爵茶"，如：Earl Grey tea is a world favourite and very popular here in Australia, while in China the market is still young. 伯爵茶是世界上人们最喜爱的一种茶，在澳大利亚很受欢迎，而在中国市场上仍然很年轻。
diurnal: adj
表示"每日的；白天的"，如：A diurnal animal hunts its food during daylight.白天活动的动物在白昼时猎食。
lark: n
表示" 云雀；百灵鸟"，如：A lark was singing high up in the sky. 一只云雀在高空中歌唱。
synchronize: v
表示" 同时发生"，如：We synchronized our watches. 我们校准了我们的手表。
receptor: n
表示"受体；接受器"，，如：Placebo effect tied to brain receptor activity. 安慰剂的效果与大脑内受体活动度有关。
chronobiology: n
表示"时间生物学"，如：Chronobiology is an emerging subject, which studies the temporal rhythm of biologic organisms and its mechanisms. 时间生物学是一门研究生物节律,即生命活动的周期规律及其产生机制与应用的一门新兴交叉性生命学科
cardiovascular: adj
表示"心脏血管的"，如：Cardiovascular disease is the leading cause of death among Americans. 心脏血管的疾病是美国人死亡的首要原因。
aerobic: adj
表示" 需氧的；有氧的；"，如：The waste water is initially stored in a series of ponds in which the anaerobic and aerobic treatment is sufficient to irrigate crops. 废水最初放置在一种池子里，使其需氧与厌氧的效应能有用地用于灌溉作物。
glucose: n
表示" 葡萄糖"，如：We injected the glucose into the patient's vein. 我们给病人的静脉里注射了葡萄糖。
intermittent: adj
表示" 间歇的；断断续续的"，means "stopping and starting at irregular intervals"，如：She suffered from intermittent headache. 她患间歇性头痛。
metabolize: v
表示" (使)产生代谢变化"，means "produce by metabolism"，如：Our bodies constantly metabolize the food we eat. 我们吃的食物在体内不停分解产生代谢变化。
ghrelin: n
表示"胃内产生的一种肽；生长素释放肽"，如：The target of the vaccine is a hormone called ghrelin. 用疫苗的话，是一种称为脑肠肽的激素。
leptin: n
表示"瘦素，瘦蛋白"，如：Leptin is correlated with insulin resistance of cirrhosis. 瘦素与肝硬化患者的胰岛素抵抗相关。
satiate: v
表示"使饱足；使厌腻；充分满足"，means "supplied (especially fed) to satisfactio"，如：He was satiated with pleasure. 他厌倦了享乐。
insulin: n
表示" 胰岛素"，如：The pancreas began churning out insulin. 胰腺开始产生胰岛素。
detoxify: v
表示"使解毒；使戒毒"，means "remove poison from"，如：Seaweed baths can help to detoxify the body. 海藻浴能够帮助解除身上的毒素。
restorative: adj
表示"恢复健康和体力的；恢复的"，means "tending to impart new life and vigor to"，如：Nature has an exhilarative and restorative effect. 大自然具有使人畅快并恢复体力的效果。
crave: v
1.表示"渴望；热望；"，means "have a very strong almost uncontrollable desire for"，如：All Americans crave to be svelte (and rich). 所有的美国人都渴望身材苗条(和富有)。
2.表示"恳求；请求 "，means "ask seriously for"，如：I crave that we may taste of your wine. 我恳求让我们尝尝您的酒。
arachidonoylglycerol: n
表示"花生四烯酸甘油"
中文简要说明：
肥胖与许多疾病有关。美国新罕布什尔州富兰克林皮尔斯大学最近发表5000人研究结果，上午7时至9时是一天之中最佳运动时段，与9时过后时段运动相较，上班前运动，一星期累计150分钟，体重少了6磅，BMI降低，饮食相对健康。英国《电讯报》以此汇整专家建议订出作息表，尤其注意咖啡、酒类摄取时段，顾好睡眠质量有利健康减重。
■上午7时起床：伦敦大学学院教授惠特摩（David Whitmore）说，每个器官的生理时钟经由大脑生理时钟同步运作，大脑生理时钟由眼睛接触光线时间而设定。睡眠专家梅多斯（Guy Meadows）建议每天固定时间起床，睡眠、进餐、接触光线时间规律，整体生理时钟可准确运作。
■上午7时20分运动：运动能燃烧脂肪与葡萄糖。富兰克林皮尔斯大学（Franklin Pierce University）研究指，一夜未进食，体内葡萄糖储量偏低，清早运动能燃烧更多脂肪，早餐前应做有氧运动40分钟，如慢跑、骑单车。
■上午10时吃早餐：多项研究显示间歇断食有助减肥，伦敦国王学院科学家建议断食间隔10小时之内。10点吃早餐比较没那么快饿，以蛋白质为主；日本研究指，上午摄取蛋白质更容易代谢，增强肌肉。晚上8时后别进食，让身体在睡前有时间消化晚餐。
■中午12时后别喝咖啡：摄取一杯浓缩咖啡的咖啡因，人体需要6小时清除。梅多斯建议睡前至少6小时别碰咖啡以防睡不好，睡眠不足会增加饥饿素（ghrelin）、降低瘦体素（leptin），让人更想进食、难有饱足感。一天喝2、3杯咖啡无妨，但限正午以前。
■下午2时补充碳水化合物：营养专家奎尔（Ulrike Kuehl）说，这个时段人体对胰岛素更敏感，消化热量成效佳，适合摄取一日所需的大部分碳水化合物。
■下午3时42分小休息：梅多斯建议，放空片刻有助夜间睡眠。2015年发表于《英国医学期刊》的研究建议，每小时从办公桌起身步行2分钟可消耗热量、保持活力，早逝风险降33%。
■下午5时肌力运动：2019年加州一项研究发现，下午4时至6时核心体温最高，肌肉关节暖身状态最好，适合举哑铃、瑜珈这类锻炼，增强肌肉兼燃脂。2018年研究显示，傍晚过后运动有助晚间更快入睡，但别在深夜剧烈锻炼或睡前运动，否则会让入睡延后1小时。
■傍晚6点吃完晚餐：奎尔说，深夜进食易拉高血糖与胰岛素浓度，不利睡眠，新陈代谢细胞活跃无法休息再生，身体就不能进入休息状态。晚餐在睡前3至4小时结束，最利减重。
■晚间8时休闲但别喝酒：运动科学家史塔基尔（Nigel Stockill）提醒，1个单位的酒精会让修复性质睡眠延迟1小时，喝一大杯红酒等于摄取3个单位的酒精。深夜喝酒，隔天起床不仅会觉得没睡好，还很想吃碳水化合物。
■晚间10时就寝：睡满8小时有助减肥。2016年研究发现，睡眠不足令体内化学物质2-AG浓度上升3分之1，2-AG会增加饮食产生的愉悦感，让人更想吃。2017年芝加哥大学研究指，提前75分钟就寝，热量摄取可减270卡（3片饼干）。就寝前宜放慢步调，制造昏暗环境，别滑手机。
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