Preventing weight regain with omega-3 fatty acids

Overweight and obesity are defined by the WHO as abnormal or excessive fat accumulation that poses a risk to health. This accumulation results from an imbalance between caloric intake and expenditure, often stemming from poor dietary habits and a sedentary lifestyle. However, obesity can also arise from various factors, including genetic, behavioral, and social influences. It significantly increases the risk of diabetes, hypertension, heart disease, and even cancer. With 17% of French adults classified as obese, a figure expected to rise by 2030, obesity is a pressing public health issue requiring urgent solutions.

Scientific literature has demonstrated that the risk of obesity is linked to the quantity of dietary fats (affecting their synthesis, transport, storage, and metabolism). However, attention should also focus on the types of fats consumed. Could the quality of fats have a greater impact than their quantity?

This question was investigated by a team of researchers, including Valorex and Bleu-Blanc-Coeur, who explored the potential relationship between the quality of consumed polyunsaturated fatty acids (PUFAs) and obesity (Legrand P et al., 2010). Specifically, they examined whether a diet rich in omega-3 fatty acids could help obese individuals lose more weight while on a diet. Although no significant impact of omega-3s on weight loss was observed during the study, an intriguing finding emerged afterward: the group that followed the omega-3-rich diet did not regain weight 150 days post-study, unlike the control group.

What are polyunsaturated fatty acids?

While it is widely accepted that saturated fats should be consumed in moderation, unsaturated fats, particularly polyunsaturated fatty acids (PUFAs), are not as well understood.

PUFAs include omega-6 and omega-3 fatty acids, both of which must be obtained through diet as the body cannot synthesize them.

  • Linoleic acid (LA), found in vegetable oils like sunflower, hemp, and walnut, is the precursor of other omega-6 fatty acids (e.g., arachidonic acid, gamma-linolenic acid). The body can convert LA into these derivatives.
  • Alpha-linolenic acid (ALA), predominantly present in plants such as flaxseed, soybeans, and walnuts, is the precursor of the omega-3 family. Its primary derivatives are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). However, this conversion is inefficient, which is why consuming fatty fish (salmon, sardines, mackerel) and seafood, rich in EPA and DHA, is recommended in addition to ALA-rich foods.

The properties of these two families differ significantly. While omega-6 fatty acids promote adipose tissue development, omega-3s can counteract obesity mechanisms by influencing lipid metabolism and reducing adipose tissue inflammation. However, dietary habits have increasingly leaned toward excessive omega-6 consumption due to their prevalence in processed foods (e.g., sunflower, soybean, and corn oils). The current omega-6 to omega-3 ratio is approximately 15:1, far from the recommended 5:1 or lower.

Which diet to use to prove the impact of the omega-6/omega-3 ratio?

The researchers hypothesized that a diet rich in omega-3s could lead to greater weight loss in obese individuals. To test this, they recruited 137 obese volunteers and divided them into two groups, each following a different diet designed for weight loss but containing the same total fat content with varying types of fats:

  • The experimental group consumed a diet with an optimal omega-6/omega-3 ratio, achieved through flaxseed meals and animal products certified by the Bleu-Blanc-Coeur label—a certification ensuring nutritional and environmental quality, partly due to flaxseed consumption by these animals.
  • The control group followed a more conventional diet with a poor omega-6/omega-3 ratio, excluding Bleu-Blanc-Coeur products.

Both groups were instructed to avoid fish and seafood, which are rich in EPA and DHA, to isolate the effects of flaxseed-derived omega-3s from animal feed on human health.

The role of omega-3s in preventing weight regain

The study’s findings were compelling in two key areas:

  • Omega-3 levels in red blood cell membranes

In fact, the amount of omega 3 in the red blood cell membranes of the experimental group increased significantly (the omega 3 fatty acid content of red blood cells is considered a tissue marker of the fatty acid composition of the diet). In addition, the levels of EPA and DHA, ALA-derived omega-3s contained in the flaxseed flour fed to the study animals, were maintained despite the very limited conversion of ALA to EPA and DHA in the body (0.5% for DHA) and in the absence of fish and seafood consumption.

The benefits of introducing flaxseed flour into animal and/or human diets are therefore clear.

Omega 3 red blood cell quantity chart
  • Anthropometric changes (weight, BMI, waist circumference) post-study

In addition, the anthropometric parameters measured (weight, BMI, hip circumference), which had fallen in an equivalent manner for all participants during the study, ultimately evolved differently after the experiment. Approximately 5 months after the study (150 days later), the control group experienced significant weight gain, BMI and hip circumference increases, unlike the experimental group. This finding suggests that omega 3s have a real role to play in preventing weight regain in obese people.

The results relating to omega-3 levels in red blood cell membranes, but above all those relating to anthropometric parameters in this study, therefore revealed a novel role for omega-3 in inhibiting weight regain, or at least preventing it. It is also important to understand that, rather than omega-3s playing a specific role, this phenomenon is more a question of improving the omega-6/omega-3 ratio (by reducing omega-6 intake, which is often excessive, or by increasing omega-3 intake). These fatty acids are processed by the same enzyme in the body, and therefore compete with each other. Excessive intake of omega-6s means that their transformation, and therefore their availability, takes precedence over that of omega-3s. Consumption of omega-6s is nevertheless necessary, but their adipogenic properties (which promote the production of fatty tissue) explain the need to limit them.

The importance of balancing omega-6 and omega-3 fatty acids is further reinforced by the observation that the diet with a low omega-6/omega-3 ratio (optimal) also contained a significant proportion of saturated fats (a lipid type to limit) yet still led to significant weight loss. Cholesterol levels (total, HDL, LDL) remained similar among participants, emphasizing the priority of achieving the correct balance of polyunsaturated fatty acids. Saturated fat quantity may thus be secondary in determining weight outcomes.

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