It’s known that restricting calories can lead to weight loss and improvement in certain health risk factors. But what is not as well understood is the influence that the quality of the diet has on these outcomes.
Some believe that a calorie is a calorie, and that the make-up of the dietary intake doesn’t contribute to weight loss. But could including more nutrient-dense foods into an energy-restricted diet improve weight loss efforts?
Despite the research surrounding the relationship between energy restriction, weight loss and metabolic health, it’s unclear what the ideal nutrient composition is to support this relationship.
Some studies look at specific macronutrient splits, dietary patterns e.g. Mediterranean diet, or add specific beneficial nutrients to the diet. However, trials that combine multiple nutrients into the diet have scarce.
To address this, researchers designed a study to examine the effects of a nutrient-enriched energy restricted diet that specifically targets metabolic health on weight loss and cardiometabolic risk factors.
A 12-week parallel-designed randomised controlled trial examined the effects of energy-restricted diets with differing nutrient quality. Participants were aged 40-70 years and had abdominal obesity – either defined as a BMI >27 and/or a waist circumference of >88cm for women and >102cm for men.
Exclusion criteria included diagnosis of diabetes prior to or during the screening process, daily alcohol intake of >20g for women and >30g for men, smoking, weight loss or gain of >3kg in the previous 3 months, diagnosis of long-term medical condition, use of medications known to interfere with glucose or lipid levels, allergy to fish oil and a vegetarian/vegan diet.
A total of 100 participants completed the intervention. They were randomised into one of three groups:
- 25% energy restricted (ER) diet with high nutrient quality
- 25% energy restricted diet with low nutrient quality
- Habitual diet (control group)
Compared to the low nutrient quality diet, the high nutrient diet was enriched with monounsaturated fats, omega-3 fatty acids, fibre and plant protein, as well as low in fructose. It included a daily fish oil supplement with 400mg EPA and 300mg DHA.
Measurements including body fat distribution, cardiometabolic risk factors, lipoproteins and fasting & post-prandial responses were taken before and after the intervention.
The high-quality ER diet induced 2.1kg greater weight loss compared to the low-quality ER diet. It also reduced fasting serum total cholesterol and plasma triglycerides and supported an anti-atherogenic lipoprotein profile.
In those who were insulin sensitive, the high-quality ER diet induced 3.9kg more weight loss than the low-quality ER diet.
The researchers concluded that with a 25% energy restriction, a high nutrient quality diet is more beneficial for cardiometabolic health than a low nutrient quality diet. It was noted that overweight insulin-sensitive subjects may experience greater weight loss from a high nutrient diet than a low nutrient diet.
However, some potential limitations were observed. There was potential bias as the subjects and dietitians could not be blinded to the intervention. The self-reported dietary intake can also lead to inaccuracies.
Further studies are required to explore how nutrient density can influence weight loss and cardiometabolic risk factors.
Schutte, S., Esser, D., Siebelink, E., Michielsen, C.J., Daanje, M., Matualatupauw, J.C., Boshuizen, H.C., Mensink, M., Afman, L.A., Fick, H. and Grootte Bromhaar, M.M., 2022. Diverging metabolic effects of two energy restricted diets differing in nutrient quality: a 12-week randomized controlled trial in subjects with abdominal obesity. The American Journal of Clinical Nutrition.