Decreasing overall fat in the regular diet can lead to small reductions in body weight in adults, which could be extremely meaningful on a population-wide scale, suggests a new study published in the British Medical Journal.

The most acceptable proportion of total fat in the human diet is still being debated. During a recent debate at the Joint Food and Agriculture Organization of the United Nations/World Health Organization (FAO/WHO), it was agreed that any consequence of total fat intake on body weight was essential to creating global recommendations.

WHO requested a systematic review and meta-analysis to examine the relationship between criteria of body fatness (waist circumference, BMI, and weight), and total fat intake in order to update the WHO guidelines on total fat intake.

Being obese or overweight heightens the risk of:

According to the study’s background information, an earlier review found no randomized controlled trials of decreased total fat intake that focused on examining the effects on weight, while a separate review found a significant relationship between weight and total fat intake.

The investigators collected results from 33 randomized controlled trials that were based in North America, Europe, and New Zealand and made up of 73,589 subjects and 10 cohort studies. The participants had differing ages and health statuses. One group of participants were on a lower than usual fat intake diet (intervention group), while the other group was on a normal fat intake diet (control group). Comparisons were made between the two groups and the effect on the amount of body fat was analyzed after at least three months.

After examination of all the trials, results suggested that diets lower in total fat decrease relative body weight by 1.6kg, BMI by 0.56kg/m² and reduce waist circumference by 0.5cm.

Each one percent reduction in energy from total fat caused a 0.19 kg decrease in body weight, compared with not changing total fat intake. This occurred in populations with 28-43 percent of energy from total fat in studies of six months to over eight years.

All of these outcomes were in trials in which weight loss was not the desired result, suggesting that they happen in individuals with normal diets.

The researchers questioned whether the decrease in weight within the low fat group was caused by participants getting more attention, time, and/or support, in contrast to those in the control group. However, when studies with more time or attention to the low fat group were taken away, the weight decrease stayed consistent.

This means the loss was actually due to lower fat intake. These outcomes were seen throughout all sensitivity examinations, implying that decreasing total fat intake produces a small, but statistically important, weight reduction, compared with normal fat intake.

Total fat reductions were associated with small, but statistically significant, decreases in cholesterol and blood pressure, suggesting an advantage of other crucial cardiovascular risk factors.
The authors concluded that decreasing total fat intake in adults can result in weight reduction, waist circumference, and BMI, compared to individuals who do not, without making any effort to lose weight.
The authors said, “it may be difficult for populations to reduce total fat intake, attempts should be made to do so, to help control weight”.