Energy needs are not the same for all people, but when energy intake (from food and drink) is equivalent to energy expended (by the metabolism and physical activity), the body is in a state of "energy balance". When energy intake is higher than energy expended, the body is in a state of positive energy balance and, when energy is expended than is ingested, the energy balance is negative. Over time, a positive energy balance will cause weight gain and, similarly, a negative energy balance will cause weight loss.
In order to maintain body weight, a perfect balance between energy ingested and energy expended is not necessary every day, but over a certain period of time (1).
Thanks to the calculations made in several scientific studies, it has been established that a positive energy balance of 100 calories a day can explain most gradual weight increase. According to these studies, the excess positive energy balance, which is known as the "energy gap", can be closed by reducing energy intake by 100 kcal/day. This prevents weight gain in people with a positive energy balance (2).
It is important to remember that these calculations indicate that an excess of 3,500 kcal generates weight gain of 0.45 kg (3).
Reducing energy intake
The main way of reducing energy intake is to reduce portion sizes and choose foods that are rich in nutrients but low in calories. Foodstuffs that are very dense in calories (relative to their volume) are considered high-energy foods and include certain types of biscuits, crackers and other sweet and savoury snacks. Foods like fruits and vegetables, which have fewer calories in the same volume, are considered low energy or nutrient dense. Moreover, the high fibre and water content in most fruit and vegetables helps to control weight, as this increases the level of satiety and reduces the appetite. With regard to drinks, there are numerous unsweetened or sweetened but low calorie beverages in the market and, of course, water (bottled or tap) contains zero calories (4).
When it comes to de reducing calories, it is important not to eliminate vital nutrients from the diet. For example, fruit and vegetables contain vitamins, minerals and fibre and certain high-calorie foods should not be eliminated from the diet as they contain essential nutrients.
Increased energy expenditure
is a key factor in preventing weight gain. Besides burning calories, it helps to keep our muscle mass
, which has a faster metabolism than adipose tissue, in good condition. When physical activity levels are low, energy intake should also be low in order to maintain the energy balance, and many adults find it difficult to achieve this balance through diet alone. For this reason, an approach based on making small changes (reducing 100 daily energy intake by 100 kcal per day and adding 2,000 steps a day) should include increasing physical activity as well as reducing energy intake (5).
It has long been established that a total of 10,000 steps a day is ideal for obtaining optimal health benefits (8). There also exists empirical evidence that demonstrates that increasing normal daily activity by around 2,000-2,500 steps results in moderate weight loss and improves blood pressure and insulin sensitivity, probably due to the loss of body fat (6).