How I nudged myself into losing 10kg in 10 months, as my doctor advised

In April last year, I found out that I was morbidly obese. While my Body Mass Index (BMI) was only slightly higher than normal, my percentage of body fat (PBF) was a shocking 29 percent. Anything above 25 percent for males is considered dangerously high. In addition, my blood pressure was borderline high and my triglycerides (a type of fat in the blood) was off the charts.

I was 86kg then. The doctor who saw me told me that I’m “morbidly obese” and recommended that I shed at least 10kg over the next year. I thought she was mad; I had not been below 80kg for nearly 20 years. So I told myself I would try to lose 5-6kg.

I have always had a self-image as a fit and healthy person. In school, I was a competitive runner; in my 20s and 30s, I took part in road races and triathlons. In the first two years of the pandemic, I hiked or ran at least twice a week. What I hadn’t realised was that my body’s metabolism had slowed and I was eating and drinking too much for my age (I turn 50 this year).

My initial reaction to the health shock was that I simply needed to step up the frequency (and intensity) of my exercise regime. Intuitively, I knew that I would need to cut down on my calorie intake. And as a behaviourist who used to be fit, I thought I had the requisite knowledge to lose weight easily.

Reality was a bit more complicated, and progress occurred more haphazardly than I had expected. In the process, I learned that some of the conventional wisdoms around weight loss were not only questionable, but may be counterproductive. I also had to (re-)learn a few behavioural insights for sustaining change. Perhaps most importantly, I found that nudges work better than shoves.

Nudge is a term popularised in Nudge: Improving Decisions About Health, Wealth, and Happiness, a book by Richard Thaler, an economist and Nobel Prize laureate, and Cass Sunstein, a legal scholar and best-selling author. It refers to an intervention which changes the “choice architecture” (the way choices are structured or presented to us) without relying on coercion or altering (financial) incentives significantly. Behavioural economists (like me) argue that nudges are often more effective than mandates and incentives in sustaining behavioural change. We also suggest that the best way to alter our behaviours is to counter one cognitive bias with another.

Consider changing defaults from opt-in to opt-out. This is often discussed in terms of organ donation. Countries with an opt-in system, such as the US, see much lower rates of participation than those with an opt-out system, such as Singapore. Changing defaults from opt-in to opt-out is a powerful nudge because it leverages our natural inertia to increase compliance or participation.

I’ll describe my weight-loss journey through five behavioural insights: the use of a commitment device; the need to counter our (natural) tendency to be overconfident with objective measures and external accountability; the recognition that small changes, accumulated over time to develop into habits, are probably more effective than major overhauls of one’s diet; the benefit of starting with achievable near-term goals; and the value of a social approach to individual change (because humans are inherently social creatures).

In particular, the BMI does not say anything about the distribution of a person’s weight: what percentage is from fat, muscle, or bone. So muscular people may have a BMI that puts them among the obese even though they have little fat. Conversely, someone who has little muscle may have a normal BMI, but still have too much body fat. As my physician pointed out, ageing might cause one to lose muscle and bone mass and gain fat around the waist, a change in body composition that would be concerning for health but might not be noticed if one focused on the BMI.

Furthermore, the BMI does not say anything about a person’s metabolic health. In a May 2021 article, The New York Times highlighted a 2016 study of more than 40,000 adults in the US, in which researchers compared people’s BMIs with more specific measurements of their health, such as their insulin resistance; markers of inflammation and blood pressure; and levels of triglyceride, cholesterol and glucose.

Nearly half of those classified as overweight (based on their BMIs) and about a quarter of those classified as obese were metabolically healthy by these measures. On the other hand, 31 percent of those with a “normal” BMI were metabolically unhealthy.

An excessive focus on BMI is harmful, the article points out, because on the one hand, doctors may ignore unhealthy habits, like a lack of exercise, in somebody with a normal BMI; and on the other, they risk stigmatising patients with a high BMI who are otherwise healthy.

The second myth is that calorie-counting works. Overweight people are often told that if they consume fewer calories than they burn each day, this calorie “deficit” would produce quick results. Governments around the world have recommended calorie-counting in health promotion policies. The World Health Organisation says that the “fundamental cause” of obesity worldwide is “an energy imbalance between calories consumed and calories expended”.

While the calorie as a measure of how much energy a food item contains is not in dispute, the emphasis on counting calories is misplaced because it ignores the fact that not all calories are created equally: different food items with the same calorific values may be digested very differently in our bodies and have different effects on our weight. Each of us also processes calories differently; even for the same person, the time of day that you eat matters. Counting calories also does not really help us to maintain a healthy diet, since the calorific value says nothing about whether it comes from carbohydrate, protein, or fat.

“...a growing body of research shows that when different people consume the same meal, the impact on each person’s blood sugar and fat formation will vary according to their genes, lifestyles and unique mix of gut bacteria,” said The Economist in “Death of the Calorie”, a 2019 piece in its 1843 magazine.

All carbohydrates break down into sugars, the body’s main source of fuel. But simple carbohydrates are very different from complex carbohydrates: the former is more swiftly absorbed into the bloodstream, giving us a quick energy boost. This creates problems when there is too much sugar in the blood. Any excess sugar not stored in the liver is converted into fat; consuming large amounts of sugar is the fastest way to get fat. And when our blood-sugar levels slump, one becomes hungry again. This explains one paradox of dieting: to lose weight a person needs willpower; the fuel for willpower is sugar; but excess sugar is what causes us to become fat. This paradox also probably explains why most studies show that in the long term, about 80 percent of people put back any weight they’ve lost.

Getting fat is also a consequence of our evolutionary past. Our hunter-gatherer ancestors would not have had many opportunities to consume sugar, so when they did come across sugar—say, during the seasons when fruits were available—they would load up on it. Over thousands of years, fat has also been a useful way for humans to store energy, allowing us to survive famine. This is one of numerous examples of how our environment has evolved faster than our minds or bodies have. Even though most humans no longer face the risk of starvation, our bodies are programmed to store excess fuel.

So if neither focusing on my BMI nor counting calories works in losing weight, what seemed to work for me?

Present bias is our tendency to value immediate costs (or benefits) a lot more than future ones. This bias arises from the fact that while I can be disciplined and rational when choosing between future options, I am much likelier to focus on immediate costs or benefits if the choice is between now and the future. For instance, I may tell myself to exercise tomorrow rather than wait till the day after tomorrow. But when tomorrow becomes today, the immediate cost of exercising weighs heavily on my mind even as the (future) benefit of exercising is excessively discounted (this inconsistency in discount rates across time is also called hyperbolic discounting). Present bias leads to inertia and procrastination: putting off something immediately unpleasant to another day.

A gym membership is a nudge: having paid upfront for an (expensive) membership, we are more likely to make use of the gym than if we were to pay each time we went. And so, I went to the gym every other day, and swam at least twice a week. It helped that the gym and the Morrison Hill public pool were minutes by foot from where I lived.

One early surprise was that I could barely complete 4km on a treadmill in under half an hour. I realised I needed another commitment device to improve my running fitness, so I signed up for a 5km race in November—about two months from that point. That should give me enough time to become race-fit, I told myself.

A crisis in late September also helped me to lose weight. The anxiety caused me insomnia; I would wake up at the crack of dawn. With sleep elusive and nothing better to do, I would run laps around the Happy Valley racecourse that was minutes from my flat.

By race day in November, I had shed about 5kg from half a year ago. I completed the race in just over 23 minutes—quite respectable for a 49-year-old, I told myself. So I thought my weight loss journey was over: I had lost the 5-6kg I wanted to lose, I was race-fit again, and I had managed to do both without cutting down on eating or drinking significantly.

In December last year, I did another health check to confirm what I had confidently assumed—that I was in good physical health. The results showed the opposite. My blood pressure had gone up, and I would now have to take medication for hypertension. My triglycerides had also not come down much despite all the running, swimming, and weight-lifting. Clearly, I had been overly optimistic that losing weight, and being able to run and swim (much) faster, would translate automatically into good health.

The second behavioural insight, therefore, is to counter our (natural) tendency to be overconfident or excessively optimistic with objective measures and external accountability. In the months that followed, I made a deliberate effort to cut down on eating (especially simple carbohydrates) and drinking. Surprisingly, this was easier than I had imagined. I did not have to engage in intermittent fasting, put myself on any special diet, or make major dietary changes. I simply ordered less, ate more healthily, and drank less frequently. By the end of February this year, my blood pressure was normal and my triglycerides were no longer too high.

And almost without realising it, I lost another 5kg in the first few months of the year. The physician who first saw me was right after all: I could lose 10kg in a year through a combination of exercise and reducing food and alcohol intake. I have been around 76kg for more than three months now.

An external accountability mechanism—in this case, physicians—was thus helpful in reducing overconfidence and excessive optimism. Their expertise not only meant that they were credible messengers, but they also validated (or invalidated) my assumptions about what worked.

The third behavioural insight I learned is that small, even imperceptible changes, accumulated over many months are probably more effective than major overhauls of one’s diet or exercise regime. Commitment devices help initially, but unless the changes become habits, they are unlikely to be sustained over time. This is why crash diets or intensive fitness regimes may produce results initially, but these improvements tend to “wash out” over time.

How do initial changes become habits? This is arguably the most challenging aspect of weight loss. A good starting point is to make small, incremental changes, which do not require a great deal of cognitive effort or willpower, and to do this consistently over time. For instance, if you’re currently exercising once a week for 20 minutes each time, try increasing it to twice a week for 25 minutes each time, and then a few weeks later, to thrice a week for 30 minutes. The idea is to make the changes small enough that they do not impose a significant psychic cost on us, and to repeat this process.

I realise that I am very fortunate to enjoy exercise intrinsically. For me, it was a case of making exercise a daily routine; I did not have to summon enormous resources of willpower, which is limited in each of us, to exercise. I also know that for many people, making exercise a daily routine would require a great deal more cognitive bandwidth and discipline—hence the criticality of keeping the changes small and incremental, and the usefulness of commitment devices.

The fourth behavioural principle I can suggest for people trying to lose weight or get fitter is to start with achievable near-term goals—such as exercising three times a week for 30-60 minutes each time. If you have an hour to spare, cycle or walk briskly; if you have 30 minutes, run at a constant pace; and even if you have only 20 minutes, work out at the gym or swim as fast as you can without stopping. I have also found that interval training adds variety and fun to our exercise regimes.

Measuring progress in itself is a form of motivation, even if progress is slow. Remember that the natural condition is atrophy, so any progress—no matter how small—is to be cherished and celebrated.

The final behavioural principle for sustaining change is to make it social. We are social creatures, not just individual maximisers. While the initial intention to lose weight or to get fit has to come from the individual, implementing and sustaining change does not have to be an individual effort. Exercising with friends is not just more fun, it’s also a (mutual) commitment device and accountability mechanism. I am incredibly fortunate to have good friends in Singapore who, when they knew of my condition, generously offered to run, swim or cycle with me. Without them, I could easily have lapsed into my old, unhealthy behaviours.

Donald is organising an 800m race on August 11th with friends and others to raise funds for the Resilience Collective (RC), a lesser-known mental health charity. Do donate. S$10 will help RC produce its mental resilience workshops. S$100 or more gets you a chance to run against the 50-year-old reliving his 30s.

Based in Hong Kong since 2019, Donald Low is senior lecturer and professor of practice, and director of leadership and public policy executive education, at the Hong Kong University of Science and Technology. He works in the areas of economics and behavioural economics, inequality and social policy, complexity in public policy, and the politics and governance of Singapore. He is the lead author of Hard Choices: Challenging the Singapore Consensus, co-written with Sudhir Vadaketh, editor-in-chief at Jom, and the co-author of PAP v PAP: The Party’s Struggle to Adapt to a Changing Singapore, co-written with Cherian George, professor at the Hong Kong Baptist University’s School of Communication.

Letters in response to this piece can be sent to sudhir@jom.media. All will be considered for publication on our “Letters to the editor” page.