I’m Dr. Emily Dhurandhar. My family has studied the science behind weight loss and have treated over 2,00,000 people for weight loss over the last several decades. I have also taught about obesity and nutrition at several universities. During these experiences, I have noticed there is a lot of misunderstanding about how weight loss works.
Understanding how weight loss works will help any effort to lose body fat. When losing weight, the real objective is losing body fat. Weight loss is just an approximate marker for fat loss.
Fat loss can be an important step towards better health. Carrying excess body fat is hard on weight-bearing joints, makes every day activities more difficult. Excess fat also increases the risk of developing chronic diseases like heart disease, cancer, and diabetes.
With a better understanding of fat loss, it becomes possible to filter through all the advice on fat loss that is everywhere. Time and efforts can be spent more wisely, through a better understanding. And you will be more likely to achieve your goals.
What is fat?
Fat tissue is made up of fat cells. Fat cells store energy. Those fat droplets contain fatty acids, which are long, compact carbon chains.
Why does the body burn fat?
The body burns fat to make energy for bodily functions and activities.
Our bodies use a molecule called adenosine triphosphate (ATP) for energy. “Fat burning” refers to breaking down fat to make ATP for energy.
Calories are a unit of energy that is used to measure the energy in food. Carbohydrate, fat, and protein in food all contain energy, because they can all be broken down to make ATP in different situations.
When does the body burn fat?
All the time! When sleeping, sitting still, resting, and during light exercise, fat is the preferred source of energy by most tissues in the body. It can also make energy from protein and carbohydrate, but neither of those is the “go-to” fuel source for the most common activities that we spend the majority of our time doing.
When does the body store fat?
After meals, fat is digested and absorbed. If it is not needed right away, it will be stored for later. If too much carbohydrate or protein has been consumed, that can be converted to fat as well, and stored.
The fat burned in a day is about equal to the fat stored in the body. That is why fat stores are fairly constant, from day to day.
What makes fat loss happen?
A major disruption in the number of calories eaten is the only way to cause fat loss.
Normally, a healthy person consumes as many calories as they use each day. The fat used up gets replaced almost immediately. This happens automatically.
To make the body lose fat, more calories must be used than what is consumed in the diet. This state is called “negative energy balance,” because the body is at a net loss for energy. The fat burned will not be replaced by the diet, and fat loss will happen.
How to create negative energy balance
Eating less food is the way to cause negative energy balance. That way, the body is consuming fewer calories than it burns. Fat is the main source of energy to prioritize first and it gets used up. In theory, it is that simple.
But in practice, it is not so simple. Here is why.
Losing Weight is A Battle with the Body
Losing weight isn’t a normal, natural process. To understand why, take a deeper dive into an extreme example. Eating less causes weight loss. So, if someone were to stop eating, would they eventually disappear into thin air?
No! Because survival depends on having a body. If there was no swift and extreme adaptive response to starvation, no one would survive for very long.
And in fact, there is a response to even a more moderate form of starvation such as a weight loss diet. When weight starts to drop because of an intentional reduction in food intake, the body fights back. Hunger, mood changes, head aches, and fatigue are common. The energy expended to maintain the body also decreases, as the body becomes more efficient to conserve energy.
These side effects of weight loss that make it a battle can be managed. A diet that is higher in protein and fiber is one strategy that can help trick the body. This type of diet can lessen the side effects of weight loss.
Getting Enough Nourishment
One challenge when reducing food intake to lose weight is giving the body enough nourishment. There are 40 essential nutrients that are needed for survival. Eating less food, while still getting enough of those essential nutrients, requires some nutrition knowledge and skill.
This is complicated by certain conditions that require special attention to specific nutrients. For example, if someone has low bone density and is at risk of osteoporosis, the diet needs to be sufficient in calcium and Vitamin D. Or, if there is iron deficiency, the diet cannot be deficient in iron.
Another challenge is reducing food intake in the right amounts from one food group to the next. Some nutrients are only present in certain foods. So if that food or group of foods is cut from the diet, that can lead to a deficiency of that nutrient. And nutrient deficiencies can worsen your health.
Consistency and Control
Losing body fat requires a consistent reduction in calorie intake, week after week. But there are some days or weeks where that seems impossible. For example, weddings, vacations, and other life events often involve food-related traditions. There are times when you just cannot control what food you are eating.
There are also challenges to knowing how many calories you eat on a daily basis. Perhaps someone cooks for you, and you aren’t sure what is going into your food. Or, maybe you have a fast-paced lifestyle that relies on restaurant food.
Maintaining some consistency in controlling your food intake requires a special effort and sacrifice. There will be setbacks, and it is important not to be discouraged by those setbacks. Remember, even if it doesn’t go perfectly all the time, everyone trying to mind their calorie intake is still doing better than if they weren’t paying any attention at all!