• Emilina Lomas

How to lose weight according to science

Did you know that 40 percent of the US population is obese, and an additional 30 percent are overweight? There’s no wonder as to why almost half of US adults are on a diet at any given time according to the US Centers of Disease Control and Prevention. So if this applies to you, this article will give you the science behind weight loss, the best weight loss tips, weight loss exercises, the role of your metabolism and teach you about your basal metabolic rate so you can improve your health, and life, for good.



First of all, it is important to understand the difference between weight loss and fat loss. Your body weight measures total mass (fat, water, bone, muscles and organs), whereas your body fat just isolates the amount of adipose and visceral fat. It’s important to understand this distinction, because body fat is the most accurate indicator and predictor of well-being and disease, whereas body weight and health are not always negatively correlated, meaning you can weigh more than average, but be healthier than average too.


How is weight gained and lost?


Body fat is gained when you have a positive energy balance for a prolonged period of time, as explored in a study published by the Proceedings of the Nutrition Society in 2003. This essentially means that your energy intake is higher than your energy expenditure - you’re eating too much and you’re not moving enough. The extra calories consumed are stored as they are not needed for energy, they will be stored as triglycerides (fat) and glycogen (carbohydrates stored with water). Thus, any increases in body weight are as a result of excess calories and increases in water retention.


Research shows that individuals at a healthy weight must be able to maintain a zero energy balance, which means energy is equal to energy expended. If you are in a negative energy balance, you will lose body fat because your body will be metabolizing energy stores.

This has been shown in a study by Swinburn et al in which researchers assessed the change in calorie intake and average body weight from the 1970s to 2000. When comparing the change in average weight, the calculations equated almost exactly to the increased calorie intake, proving that calories matter, too much of them and you will gain weight rapidly.


What is your metabolism?


You have probably heard someone tell you that weight loss comes down to calories in vs. calories out. While this is not exact science, it is useful to view weight loss this way. This is the role of your metabolism. The scientific definition of your metabolism is the chemical processes that occur to maintain life, i.e. it controls how you use the energy you consume through food, and how much you need to maintain functionality. A fast metabolism will burn through energy quickly, while a slow one will promote fat storage, but to clear up some of the confusion when it comes to the metabolism, neither of these are ideal. A healthy metabolism is preferred, as it will help you to maintain a healthy body weight and use energy efficiently.


To understand how many calories you burn in a day (your total daily energy expenditure TDEE) you first have to calculate your basal metabolic rate (BMR) using a BMR calculator like this one. When you know this figure, you can set caloric and macronutrient targets that will allow you to lose weight.


Based on the most up to date research, your TDEE is comprised of four main components:


  • Basal metabolic rate (BMR) the definition of your BMR is how many calories you burn at rest and it makes up the largest contributor (70 percent) to your TDEE

  • Non-exercise activity thermogenesis (NEAT) which includes walking, hand gestures and any activity that is not exercise based, and makes up 25 percent of your TDEE

  • The thermic effect of food (TEF) which is the calories burnt from digesting the food you have consumed throughout the day, accounting for 10 percent of your TDEE

  • Exercise activity thermogenesis (EAT) which is the amount of calories burnt during exercise, accounting for only five percent of your TDEE


Your TDEE is calculated using important metrics that differ from person to person, these include: your height, weight, age, gender, activity level and body fat percentage. If you eat more than your TDEE you will gain weight, and if you eat less than your TDEE you will lose weight.


Once you have calculated your TDEE, minus 300 to 500 calories. The number you are left with is how much you should be eating daily to lose weight. These caloric targets will put you in an energy deficit, meaning your body is forced to break down fat stores for energy. This energy deficit must be created through food intake, but can be accelerated by increasing your energy expenditure through exercise too.


Weight loss tips


The best weight loss tip is to alter your diet, consuming less calories than you are burning. To ensure you are not overeating, it is a good idea to track what you eat. You can do this by downloading an app like MyFitnessPal and inputting your calorie targets (based on your TDEE and BMR using an online calculator). An 8 week weight loss trial found that dietary self-monitoring (macro tracking) was associated with increased weight loss than a control group. A systematic review that looked at 30 apps for tracking calories found that the apps helped to improve motivation, reduce stress and improve adherence to weight loss.


In terms of what you should be eating, it’s best to focus on whole foods and a moderate to high protein intake. Research shows that a high protein diet is the most effective for fat loss because protein consumption increases the speed of your metabolism, increases satiety and reduces appetite. It does this by boosting thermogenesis i.e. the thermic effect of food (TEF) as mentioned in the section about your TDEE. Essentially protein is harder to process than fat or carbs, with up to 35 percent of the total calories consumed being used immediately, just to digest it. By default, this boosts your metabolism. Studies show that high protein caloric deficit diets preserve lean body mass and maintain a higher basal metabolic rate. When also combined with regular exercise, this puts you in an optimal, accelerated environment for fat loss.


You can also increase your energy expenditure through exercise, to further push you into a caloric deficit to accelerate weight loss. The best types of exercise for weight loss are high intensity interval training (HIIT) and strength training. These two types of exercise increase your metabolic rate for hours post-workout so you will be burning calories faster and again, increasing the deficit. A 2012 randomized controlled trial that lasted for a year looked at whether diet, exercise or both combined was most effective. The researchers found that the average weight loss was highest in the diet and exercise group (10.8% of body weight), compared to diet (8.5%) and exercise (2.4%). So combining a healthy diet and exercise will make weight loss way easier!


But you shouldn’t just exercise to lose weight. Exercise benefits are extensive: studies show that individuals who regularly exercise have a 35 percent decreased risk of developing heart disease or stroke, a 50 percent decreased risk of developing type 2 diabetes and obesity, age slower, have less age-related illnesses like sarcopenia, and experience less mental health problems. So even if your main focus is not weight loss, exercising regularly is important for maintaining good enough regardless.


If you want to lose weight for good, follow the weight loss tips outlined in this article to enjoy consistent results without the confusion or stress. Calculating your BMR and TDEE will allow you to set proper caloric targets, tracking your food intake, eating a high protein diet and regularly exercising will guarantee weight loss. So forget diet pills or the weight loss myths you’ve heard, this is how to lose weight according to science.


  • Facebook
  • Instagram