The great January math

The past year’s indulgences are officially forgiven and declared over. January is redemption time. Gym classes are booked at a discount, because ’tis the season. Salad bowl subscriptions may burn more money than fat, but one must try.

The white pantry is stocked with brown rice, brown bread, brown sugar, and multigrain products. Mornings will begin with anti-inflammatory drinks. Vision boards will become the voice of conscience, reminding us that weight loss is 90% mindset. Nights will end watching body transformation reels, for motivation or guilt, it’s hard to tell.

At the centre of this reset, earnest, absurd, and exhausting, sit calories.

Invented as a unit of heat energy, it now dictates what people eat, how they feel, and what discipline looks like. And like Bridget Jones, they convince themselves that if they count calories carefully enough this time, their body will finally change.

However, experts based in Bengaluru say the ‘calories in, calories out’ approach isn’t straightforward. Nor is it sustainable, as the New Year's josh often fizzles at one scoop of ice cream. If you want results that last, keep it old-school: eat well-rounded meals, move more, get enough sleep, and drink plenty of water.

Is calories in, calories out 'legit'?

Rebecca Kuriyan Raj, professor and head of the division of nutrition at a research institute, says weight management is multifactorial. At its simplest, eat as many calories as you burn, and your weight stays steady. Eat more than you burn, and you gain. Burn more than you eat, and you lose weight. The catch? People aren’t great at tracking what they eat.

There’s often a 30% error in dietary recall, including both overestimation and underestimation. Also, remember that 50-60% of the calories you burn are used to fuel your body at rest — for breathing, circulating blood, repairing cells, and maintaining body temperature. This is called your Basal Metabolic Rate (BMR). BMR is fairly constant, so to create a calorie deficit, you need to eat less or move more, she says.

According to dietitian Edwina, your overall calorie-burning ability, or metabolism, can vary widely based on factors like age, gender, physical activity, and even weather. Conditions such as hypothyroidism or PCOD, or the use of steroids, can affect muscle mass, which in turn can lower metabolism. The gut microbiome may also influence appetite hormones and the energy we burn during weight training, but she says larger studies are needed to confirm these theories.

Sometimes, managing blood sugar and getting enough sleep can achieve what calorie tracking alone cannot, says sports nutritionist Deepika Vasudevan. “In my practice, I have seen women with pre-diabetes or insulin resistance (where food isn’t fully utilised) lose weight simply by eating balanced meals and managing stress. They also woke up feeling fresh and energetic,” she adds.

According to Anura V Kurpad, from the physiology department of a medical college, India needs more research to accurately measure activity-related energy expenditure (the amount of energy burned by the human body). He poses a simple question: “When someone goes for a run, do they negate it by being sedentary (for the rest of the day) because they feel they have ‘done their bit’?”

Who should not count calories?

“Not children or teenagers, but adults in their 20s and beyond can. And certainly not anyone struggling with eating disorders like bulimia,” says Deepika. Edwina says during illness, skip the calorie count because your body needs fuel to heal.

Gautham Sangappa, director of a fitness academy, says counting calories depends on your goal. “For athletes, it’s unavoidable. Overeating or undereating, the quality of calories, and even when they eat, can show up in their very next training session. It is tied to their performance outcome.” But for the average person, this level of hair-splitting isn’t necessary, except for those hitting repeated fat-loss plateaus or those recovering from disordered eating patterns.

Are all calories the same?

Whether 100 calories come from 11 g of fat or 25 g of carbs, the number is the same. “But if you look only at numbers, you can’t plan a balanced diet,” says Edwina. The body is a complex machine that needs macronutrients (carbs, proteins, and fats) and micronutrients like vitamins and minerals in the right balance to perform optimally and maintain good body composition.

Edwina says that rather than just chasing calorie counts, the focus should be on the nutritive value of food. “For example, 15 g of nuts provides about 80 calories. But it also provides 7 g of essential fats, which can supplement the body’s requirement.” She adds that what constitutes a balanced diet varies depending on individual needs and health conditions.

Rebecca reminds us that we are living in an era of calorie-dense packaged foods. A 50 g apple contains about 100 calories and is rich in vitamins, potassium and fibre, while a 50 g pack of potato chips packs nearly 250 calories along with unhealthy fats. An apple, with its fibre and water content, keeps you full longer, whereas ultra-processed chips are absorbed quickly and encourage overeating.

Sangappa reiterates that the source matters and adds, “If you are waking up tired despite meeting your calorie intake, you could be low on iron or calcium.”

Fat or muscle loss?

What you exercise and what you eat afterwards decide what you lose, stubborn fat or precious muscle. Deepika shares, “Brisk walking actively burns calories and fat. Cardio, like running or dancing, can burn muscle. But if you follow it with protein-packed paneer bhurji rather than a masala dosa, your body is more likely to lose fat than muscle. Strength training builds muscle, which helps burn calories at rest.”

Carbohydrate conundrum

According to Rebecca, carbs have always made up 60-70% of the Indian diet. Much of this came from complex carbs with high fibre content. But now, we are eating bigger portions, calorie-dense foods, and more refined carbs. In an unpublished study at her institute, they tried cutting carbs by 20% in a typical diet to see its effect on weight maintenance. Those who stuck to it did see positive results.

Kurpad elaborates on the ongoing debate about whether body weight can be manipulated by diet composition — low carbs versus low fat — rather than by total energy (calorie) intake. This is known as the Carbohydrate-Insulin Model (CIM) versus the Energy Balance Model (EBM). The CIM suggests that low-carb diets trigger less insulin than low-fat (high-carb) diets. Since insulin promotes fat storage, lower insulin levels may make it easier to burn fat. Low-carb diets also increase energy expenditure. The EBM, however, emphasises that the basic rule still applies: energy intake must match energy needs — eat more than you burn, and you gain weight; consume less, and you lose weight.

Calorie deficit in women

In her practice, Deepika often sees women in their mid-20s and above, mostly from upper-middle-class families, asking for calorie-deficient diets without realising they are already undereating. “Adult Indian women should eat 1,600-1,800 calories a day, but many barely reach 1,200-1,400, which are toddler portions,” she says. In the morning rush to send kids to school or head to work, many skip breakfast or survive on coffee. This triggers a cortisol spike that can lead to more fat storage later in the day.

Fitness tracker says I burned 100 calories. Did I?

According to Sangappa, fitness trackers can have a margin of error of 10% or more. They might log 500 steps fewer than you actually take. But even so, the numbers can motivate you to reach your target. The gap is that trackers only measure calories you ‘burn’. They don’t automatically track what you eat, from the oil you cook with to the mayo, ketchup, and chutney you go back for seconds. They also don’t account for how well you rest, how hydrated you are, or your life stressors. All of these affect hitting a calorie deficit.

“One of my female clients was doing everything right — 5 km runs, resistance training, cardio. But she started gaining weight. It turned out her stress levels were through the roof. She was in a managerial role and barely slept five hours a night. So instead of cutting calories, we asked her to eat a little more, rest properly, and reduce workouts. Her fat levels came down,” he says.

Deepika says calorie burn is unique to each person, but trackers rely on generalised formulas based on heart rate, during activity and at rest, of an average individual. That’s why they can’t capture the full complexity of each body.

Are calories on food labels accurate?

Edwina says that when foods are lab-tested, the numbers are mostly reliable. However, she urges caution with zero-calorie drinks. The artificial sweeteners they contain aren’t calorie-free in effect, and have been shown to upset gut health or spike blood sugar.

But labelled calories may not always equal calories absorbed. A 2021 University of Toronto study found that about 20% of the calories in almonds, mainly from fat, went unabsorbed, resulting in 2% lower energy intake overall.

How quickly can I slim down without starving myself?

According to Sangappa, losing 10 kg in a month is possible, but most of that would be water or glycogen (stored sugar) loss, or even muscle loss. Real fat loss takes time. A sustainable approach typically involves a daily calorie deficit of 200-500 calories. “This translates to about 0.5 to 1.5 kg of fat loss per month. The initial weeks may show faster scale movement due to water loss, but the rate naturally slows as the body adapts, and you will need to step up your workouts,” he explains.

A combination of resistance training, cardio, and proper rest boosts metabolism and lets you steadily achieve a 10 kg loss over 6 to 12 months. He says every January, signups at his academy spike by 50%. Most newcomers dream of shedding 10 kg in two months, but 8 out of 10 quit within a fortnight!

When did we start counting calories?

The calorie obsession has surprisingly unglamorous origins. It began on factory floors. In the 19th century, as industrialisation and large-scale agriculture took hold, scientists began studying the relationship between the body’s energy expenditure and work output. ‘Counting Calories’, a 2011 article on the Science History Institute’s website, sheds more light.

In Germany, studies of human fatigue had become part of managerial science. Across the Atlantic, similar experiments were underway. In Massachusetts and Connecticut, chemist Wilbur Olin Atwater calculated how many calories and nutrients the bricklayers needed to sustain hard labour. Brickyard managers used such findings to decide which diets would “promote the largest production of brick per man at the lowest cost to the employer”.

The word calorie was largely confined to laboratories. And when it did arrive on the scene during World War I, it caused some confusion. Was it a new breakfast item or an explosive, the American public wondered? To save food for soldiers, the US Food Administration warned that eating more than the recommended calories for one’s age, sex, and activity level undermined the war effort. Soldiers received more calories than civilians. In New York City, restaurants even posted calorie counts on menus as an act of patriotic duty.

But calories truly captured the imagination of Americans, especially women, in 1918 with ‘Diet & Health: With Key to the Calories’, the first weight-loss bestseller. Its author, physician Lulu Hunt Peters, described how cutting calories led to weight loss, drawing on her own experience of losing 70 pounds (about 31 kilos) in her forties. So convinced was she that she even taught readers to pronounce the word (Kal’-o-ri) and think of food as numbers, eating as arithmetic, and self-control as virtue. “Instead of saying one slice of bread, or a piece of pie, you will say 100 calories of bread, 350 calories of pie,” she wrote in the slim guidebook. At a time when beauty ideals were shifting from plumpness to thinness.

Calorie counting returned to the centre of the debate in the 1980s. According to Kurpad, the obesity rates in Western countries rose alongside the industrialisation of the food chain and the easy availability of energy-dense, highly processed foods. “The question then was whether individuals were personally responsible for weight gain (fat inactive slob who should eat less, exercise more) or whether weight gain was driven by constitutional factors in their body, making it ‘not their fault’,” he explains.

Thinking oscillated between two poles. Drugs designed to suppress appetite or increase energy expenditure reflected the ‘not your fault’ view, whereas calorie counting emphasised personal behaviour and responsibility. Neither approach worked well in the long term. The drugs failed to deliver consistent results, while calorie counting ran into the brickwall of adaptation (as you ate less, body became inactive to conserve energy).

How calories in food were calculated

At first, calories had nothing to do with food. It belonged to boilers, furnaces, and the science of thermodynamics. It is defined as the energy (heat) needed to raise the temperature of 1 gram of water by 1°C. The term, from the Latin calor (heat), was introduced in the early 1800s by French physicist Nicolas Clément-Desormes. He used it in lectures to quantify the heat energy derived from fuels like coal to power steam engines.

‘Calorie,’ a year-long exhibition going on at Science Gallery Bengaluru, traces the experiments that established the food calorie — the measure of energy your body derives from food.

The shift from machines to metabolism had already begun thanks to Antoine Lavoisier, the father of modern chemistry. The French chemist wanted to understand where body heat came from. He placed a guinea pig in an ice-filled container and measured how much ice melted as it breathed. Respiration is a slow combustion, similar to burning charcoal, he concluded. Once life was understood as a kind of engine, it seemed natural to measure its fuel, food.

By 1831, Germany’s Justus von Liebig developed an apparatus to measure carbon, hydrogen, and oxygen in organic samples. Irish chemist Thomas Andrews burned food in a chamber and tracked the heat released into surrounding water. The next leap came when British physician Edward Smith turned these techniques on humans, measuring the oxygen they inhaled and carbon dioxide they exhaled inside a room-sized chamber. It was a seminal work in understanding human metabolism and exercise physiology.

Towards the end of the 19th century, the scene shifted to America, where chemist Wilbur Olin Atwater and physicist Edward Bennett Rosa conducted tests in a massive respiration calorimeter. Participants ate, worked, and slept inside a temperature- and ventilation-controlled chamber with just enough room to pace, and a folding bed, chair, and table. Food and drink were passed through a small opening, and waste removed the same way.

Atwater’s experiments confirmed what had been observed in animals: humans obey the first law of thermodynamics. Energy from food is not lost. It is either used for activity and rest or stored in the body. He standardised caloric values for macronutrients — protein (4 kcal/g), carbohydrate (4 kcal/g), and fat (9 kcal/g). This Atwater system formed the basis of modern calorie counting and nutrition labelling. He also showed that alcohol could be oxidised for heat like carbohydrates. This insight was exploited by the liquor sector to promote drinking, much to his dismay.

Food versus research

In the world of food and fitness, a calorie actually means a kilocalorie (that’s 1,000 calories). It is also called a large calorie, food calorie, dietary calorie, or kilogram calorie, and it measures the heat required to raise 1 kg of water by 1°C. The small calorie is used in chemistry and physics, and is a measure of the heat needed to raise 1 g of water by 1°C. To distinguish, the food calorie is sometimes written as kcal or Cal (uppercase), while the scientific calorie as cal (lowercase).

Recommended daily calorie intake in India

Adult men typically need between 2,110 kcal (sedentary) and 3,470 kcal (heavy work), while women require 1,660 kcal and 2,720 kcal. Rural populations are allotted slightly more calories (around 2,400 kcal) due to higher physical activity compared with urban areas (about 2,100 kcal). The 2024 ICMR-NIN dietary guidelines recommend a balanced diet with 50-55% of calories from carbohydrates, 10-15% from proteins, and 20-30% from fats. According to their ‘My Plate for the Day’ guideline, half of your plate should have fruits, vegetables, and tubers, a quarter of cereals and millets, another quarter of pulses, flesh foods, eggs, nuts, or dairy, plus oils and spices.

Beyond pop culture

A calorie is not just the number on the back of a chips packet, what you rack up on a fitness tracker after 10,000 steps, or the daily target your dietician asks you to meet. It is also an invisible force shaping politics, economics, labour, culture, and memory.

‘Calorie’, a year-long exhibition and engagement at Science Gallery Bengaluru, strips the food on our plates down to its ground realities. Why should we care? Because, as the exhibition notes, “the desire to eat and satiate hunger drives us from the moment we are born”.

The exhibition nudges us to think how palm oil is driving deforestation and displacement, how famine, war, and caste have shaped culinary practices, and how Britain’s bid to break China’s monopoly made tea an obsession in India.

For this writer, one of the most revealing sections is the photo series ‘What I Eat: Around the World in 80 Diets’. Individuals from different countries are pictured alongside a typical day’s worth of food. Their calorie counts vary: a young Internet gamer in China consuming 1,600 kcal, a Sudanese refugee and an unemployed American at 2,300 kcal each, a brewmaster in Germany at 2,700 kcal, a woman farmer from Ecuador at 3,800 kcal, and a yak herder in Tibet at 5,600 kcal. The images bring into focus how personal dietary choices are often at odds with ideal prescriptions of what is considered “healthy” or “adequate”, shaped instead by access, work, lifestyle, environment, and climate.

Food politics is a recurrent theme in the exhibits, talks, and workshops. From measuring hunger and poverty to deciding staple crops, policy has long intersected with what we eat. One talk traced how, in the 1970s, efforts to standardise an affordable Indian diet placed low-cost plant foods at the centre. As a result, diverse regional food practices were flattened, and the role of animal protein in many communities overlooked. The loss is stark. India once cultivated over 2,00,000 varieties of rice, but today most Indians consume barely 15. On some fronts, course correction has set in. Governments and scientists are fortifying the nutrients that were lost when we switched to refined flour and fast-acting yeast to make commercial white bread.

The exhibition also examines contemporary anxieties. Are we becoming “carbivores”? A recent ICMR-INDIAB study shows Indians derive 62% of daily calories from carbohydrates, while protein intake remains suboptimal at 12%. Ten-minute food deliveries provide instant gratification, but at what cost to gig workers? And who really burns the calories — the consumer or the delivery agent? As food insecurity grows, could indigenous practices such as eating insects enter the mainstream as alternative protein sources? And why does malnutrition persist in a country of agricultural abundance?

Among its pressing questions, the exhibition also makes us introspect our relationship with our bodies. In ‘Stuff Change’, visitors can hear the rumble of the gut through an inflatable sculpture. But these ‘embarrassing’ sounds are a sign that the body is at work, digesting food and extracting the energy (calories) that fuel us.