Weight loss is often associated with strict diets, long hours at the gym and giving up favourite foods. But sustainable fitness does not always require extreme measures. Small, consistent changes in daily habits can often make a bigger difference, especially for people trying to balance their health goals with demanding work schedules. Tamannaah Bhatia's fitness coach Siddhartha Singh recently shared a simple approach that helped an investment banker in New York lose 13.8 kg in 90 days, without relying on starvation or detox diets.How an Investment banker loses 13.8 kg in 90 daysSiddhartha Singh, known for his functional training and science-based approach to fitness, shared the transformation on Instagram. According to the trainer, his client, identified as S, managed to lose 13.8 kg over three months while continuing to work in a demanding investment banking job in New York.Sharing the details of the transformation, Siddhartha said the plan did not involve detoxes or extreme food restrictions. Instead, the focus was on adequate protein, regular movement, structured workouts and consistency.The trainer explained that the goal was not to force the client to completely change her lifestyle. Rather, the fitness plan was designed to fit into her existing routine, making it easier to follow even on busy workdays.1. Structured strength trainingThe first habit Siddhartha talked about was strength training. However, he pointed out that simply following random workout videos online does not necessarily amount to a proper strength-training programme.According to the trainer, many people believe they are doing strength training because they occasionally perform exercises they find on Instagram or YouTube. However, he stressed that a proper programme needs structure. Having a planned routine, he explained, helps create consistency and ensures that the workouts are followed in a more organised manner.For S, strength training was therefore not about randomly choosing exercises each day. The workouts followed a structured plan that could be maintained over time.2. Eating enough proteinThe second important part of the plan was protein. Siddhartha said many people, particularly women, believe they are eating enough protein but may realise they are falling short when they actually calculate their daily intake.He explained that simply eating one protein-rich meal a day may not be enough to meet the body's requirements. According to the trainer, inadequate protein intake can also contribute to frequent cravings, which may make it more difficult to stay consistent with a fitness plan.For the investment banker, ensuring adequate protein intake was therefore an important part of the transformation. The focus was on making protein a regular part of the diet rather than treating it as an occasional addition.3. Walking and daily movementThe third habit was walking. The client was given a daily step goal, but Siddhartha's approach was not about completing all the steps at once.He explained that walking is useful because it allows people to add movement to different parts of the day. Instead of trying to complete a large number of steps in a single session, people can gradually accumulate them while going about their regular routine.The trainer said this type of fragmented movement helps people remain active throughout the day. For someone with a demanding office job, adding short periods of walking can be more practical than trying to find time for a long workout every day.Why accountability mattersSiddhartha also credited accountability as an important part of the transformation. Having a coach to guide the client throughout the process helped her remain consistent and stay on track, even when work became demanding.The trainer's broader message was that fitness does not necessarily require a complete lifestyle overhaul. Instead, a structured workout plan, sufficient protein, regular movement and consistent support can help people work towards their goals.