Do Low Calorie Diets Work?

Nope. And here’s why.

This model is defined by the advice to eat less and move more to lose weight. This shifts the blame to the patient, insinuating that if they just had a little more will power, they’d be able to achieve their desired weight loss goals. However, more and more evidence is coming to light that it’s not HOW MUCH we eat, but rather WHAT we eat that drives sustainable and long term weight loss.

The “calories in, calories out” model of weight loss is comparable to the idea of a sink that collects all the calories you eat in a day. It says that calories are pulled from the sink for energy regardless of whether they come from carbohydrates, proteins or fats. By this logic, simple caloric reduction should be enough to stimulate weight loss. Put less in the sink, and the body will have to dip into its fat stores to keep producing energy and support metabolism. Right? Well, let’s look at the science.

What does the research say about low calorie diets?

In the short term, caloric reduction below what we need to sustain our current weight (known as your basal metabolic rate multiplied by a factor for activity level) does result in short term weight loss. This makes sense: eat less than you need, and you have to break down what you have stored, resulting in a lowered body weight.

However, as some researchers point out, “Why is a reduction in calorie intake recommended when a lower energy intake leads to hormonal changes that stimulate appetite, reduces metabolic rate, and stimulates the consumption of more calorific foods?” From an evolutionary standpoint, the human body is great at replacing lost weight, but falters when told to keep weight off. When in a calorie deficit, humans have been shown to subconsciously do all they can to make up lost calories.

Other physiological changes occur as well. One review concluded that “diet-induced weight loss results in long-term changes in appetite gut hormones”, leading to “increased appetite and weight regain”. Essentially, the brain will do all it can to increase appetite to replete calorie deficit. The body wants to remain in a state of homeostasis, making it difficult to achieve a new set weight.

There are many things to consider when we are talking about weight loss that are beyond just the number of calories consumed in a day. One study found that the size of a meal was impacted by eating with others, hunger, thirst, happiness and anxiety. This shows that the amount we eat in a meal or a day is not static, but fluid. These findings also point out that the act of eating has a profound psychological impact that cannot be ignored, but often is when talking about calorically restricted diets.

Need more proof? Studies show that one third to two thirds of dieters regain more weight than they lost while on a calorically restricted diet.

What’s the bottom line? To put it bluntly, diets make you fatter, hungrier, and lead to increased appetite.

So, is there a better way to lose weight?

Yes!  First of all, we find that it’s important to do some self-reflection about body image and weight loss. Health comes in all shapes and sizes. Before setting a goal to lose weight, it can be beneficial to simply look at the way you are currently eating and set a goal to improve the nutrient density of your intake and ensure you are eating in a balanced way.

Once you do that, you may not even feel the need to count calories or macronutrients and you end up having more freedom when it comes to food as well! If you identified a true need for weight loss (maybe due to a diagnosed medical condition), it’s a good idea to work with someone who has your long-term goals in mind and can help you achieve safe and sustainable weight loss over time.

Sustainable weight loss may be easier achieved by looking at how we metabolize and store carbohydrates, fats and proteins. This approach is much more nuanced and is linked with sustainable weight loss over the long term. One controlled feeding study found that the reduction in energy metabolism associated with low calorie diets was highest with a low fat diet, and the lowest on a low carbohydrate diet. This shows that the macronutrient breakdown of our daily caloric intake may have a significant effect on weight loss beyond total calories consumed.

A significant downfall of calorie restricted diets is that they don’t take into account the nutrient density of food. If someone is told to follow a 1200 calorie diet they may choose to fill their day with “diet” foods, 100 calorie snack puddings and artificial sweeteners and eschew a more whole foods focused approach. Ignoring the vitamins, minerals, nutrients and antioxidants present in food is a problem because over time, nutritional deficiencies can occur. If the body does not have the proper nutrients to support energy metabolism and regulate blood sugar, weight loss may not occur.

Eating in balance allows food freedom and avoids feelings of restriction. A good rule of thumb is to try to identify the following every time you eat: a fiber rich carbohydrate or starch, a non-starchy vegetable, a healthy fat and a protein. Make half your plate a non-starchy vegetable, a quarter protein and a quarter either a starch or extra veggies.

A final thought: obesity is not a one solution problem

Finally, it’s a mistake to think that the problem we have in America regarding obesity is merely due to excessive caloric intake. There are many pieces of the puzzle and they need to be addressed in a collaborative way. In particular, psychological, social, economic and hormonal factors that drive obesity must be also be identified. Additionally, supporting a healthy and positive relationship with food is vital to long term success with weight loss. This coupled with a nutrient dense, macronutrient balanced diet is a great place to start.

Sources:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5639963/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4827002/

https://pubmed.ncbi.nlm.nih.gov/17469900/

https://pubmed.ncbi.nlm.nih.gov/30429127/

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  • Diabetes Program
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  • Diabetes Program
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  • Food Sensitivities
  • General Information
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