We hear about calories all the time. How many calories are in this cookie? How many are burned by 100 jumping jacks, or long distance running, or fidgeting? But what is a calorie, really, and how many of them do we actually need? Calories are a way of keeping track of the body's energy budget. A healthy balance occurs when we put in about as much energy as we lose. If we consistently put more energy into our bodies than we burn, the excess will gradually be stored as fat in our cells, and we'll gain weight. If we burn off more energy than we replenish, we'll lose weight. So we have to be able to measure the energy we consume and use, and we do so with a unit called the calorie. One calorie, the kind we measure in food, also called a large calorie, is defined as the amount of energy it would take to raise the temperature of one kilogram of water by one degree Celsius. Everything we consume has a calorie count, a measure of how much energy the item stores in its chemical bonds. The average pizza slice has 272 calories, there are about 78 in a piece of bread, and an apple has about 52. That energy is released during digestion, and stored in other molecules that can be broken down to provide energy when the body needs it. It's used in three ways: about 10% enables digestion, about 20% fuels physical activity, and the biggest chunk, around 70%, supports the basic functions of our organs and tissues. That third usage corresponds to your basal metabolic rate, a number of calories you would need to survive if you weren't eating or moving around. Add in some physical activity and digestion, and you arrive at the official guidelines for how many calories the average person requires each day: 2000 for women and 2500 for men. Those estimates are based on factors like average weight, physical activity and muscle mass. So does that mean everyone should shoot for around 2000 calories? Not necessarily. If you're doing an energy guzzling activity, like cycling the Tour de France, your body could use up to 9000 calories per day. Pregnancy requires slightly more calories than usual, and elderly people typically have a slower metabolic rate, energy is burned more gradually, so less is needed. Here's something else you should know before you start counting calories. The calorie counts on nutrition labels measure how much energy the food contains, not how much energy you can actually get out of it. Fibrous foods like celery and whole wheat take more energy to digest, so you'd actually wind up with less energy from a 100 calorie serving of celery than a 100 calorie serving of potato chips. Not to mention the fact that some foods offer nutrients like protein and vitamins, while others provide far less nutritional value. Eating too many of those foods could leave you overweight and malnourished. And even with the exact same food, different people might not get the same number of calories. Variations in things like enzyme levels, gut bacteria, and even intestine length, means that every individual's ability to extract energy from food is a little different. So a calorie is a useful energy measure, but to work out exactly how many of them each of us requires we need to factor in things like exercise, food type, and our body's ability to process energy. Good luck finding all of that on a nutrition label.
我哋成日聽到「卡路里」 一塊餅乾有幾多卡路里? 100 次「星星跳」可以消耗 幾多卡路里? 長跑又消耗幾多呢? 咁細嘅動作呢? 但係卡路里到底係咩意思? 仲有我哋需要幾多卡路里? 卡路里其實係我哋掌握 身體嘅能量攝取同消耗嘅一個工具 如果能量嘅攝取同消耗可以一樣 係最健康嘅狀態 如果我地攝取嘅能量多過身體所需 過量嘅部分就會被轉化成脂肪 儲存喺細胞裏面 然後我哋體重就會增加 相反,如果消耗嘅能量超過攝取量 我哋體重下降 所以我哋需要計算到我哋 身體嘅能量攝取同消耗 於是我哋就用卡路里呢個單位去計 我哋所量度食物當中嘅 1 卡路里 亦可以叫做 1 大卡路里 佢嘅定義係 1 公斤嘅水 溫度升高攝氏 1 度嘅時候 所需要吸收嘅熱量 每一種食物都有一個卡路里數值 用黎計食物入邊嘅化學鍵嘅能量 一件普通披薩有 272 卡 一塊麵包大概有 78 卡 一個蘋果就大約 52 卡 呢啲能量喺消化過程當中會被釋放出黎 然後儲存喺其他分子當中 呢啲分子可以降解 為身體需要嘅地方提供能量 呢啲能量會喺三個情況下使用 大概 10% 會用喺消化過程當中 20% 用喺身體活動度 最大嘅 70% 左右 用黎支持器官同組織嘅基本運作 第三個用途其實就係 同我哋身體嘅基礎代謝率有關 當你唔吃飯唔郁嘅時候都好 你都需要一啲卡路里去維持生命 如果加埋消化同身體活動 你就會到達指引裏邊嘅數值 就係一個人一日需要幾多卡路里 女性 2000 卡,男性 2500 卡 呢啲估算係基於一啲因素 好似平均體重、運動量同肌肉水平 咁係咪每個人嘅目標都係 2000 卡? 其實唔一定 如果你做一次劇烈嘅體能活動 譬如話環法單車賽 你身體每日就會消耗最多 9000 卡 比起未懷孕個陣 孕婦需要多少少嘅卡路里 而老年人身體代謝率通常比較慢 能量會消耗得比較慢 所以身體需要較少嘅卡路里 以下亦都係一啲你開始計卡路里之前 需要知道嘅嘢 食物標籤上面標註嘅卡路里數值 係指食物中含有嘅熱量總數 唔等於你可以從中攝取嘅熱量 芹菜同埋全麥食品呢類纖維食物 消化嘅時候需要更多嘅能量 所以如果芹菜同埋薯片都含有 100 卡 食完芹菜之後會比食薯片獲得更少熱量 唔單止噉 當一啲食物提供咗蛋白質、維他命 其他就提供唔到咁多嘅營養 如果食太多低營養嘅食物 有可能導致體重超標或者營養不良 就算係兩份完全相同嘅食物 唔同嘅人食落去都會獲得唔同嘅熱量 因為人體內消化酵素嘅數目 腸道細菌 甚至係腸嘅長短 都會影響人喺食物中 攝取卡路里嘅能力 所以,就算卡路里係有效量度熱量 但係要計每個人具體需要幾多卡 我哋需要同時考慮唔同因素 好似運動量 食物種類 同埋我哋身體消化吸收嘅能力 祝你哋以後搵食物標纖嗰陣好運