Understanding How Protein Affects Body Fat in Women
Have you ever come across the term ‘skinny fat’? The health risks of excess body fat aren’t reserved for those who are classified as overweight and obese. Some people are within a healthy weight range but still have a higher body fat percentage.
It’s well established that high-protein diets can help with weight loss. But can a high-protein diet reduce excess body fat in women with a ‘healthy’ body weight?
Why Normal Weight Obesity Matters
Normal weight obesity, or NWO, is defined as having a normal body weight and BMI, but a body fat percentage greater than 30% for women or 20% for men. Like overweight and obesity, NWO is linked to higher risks of metabolic diseases.
Studies show that women with NWO often have a lower resting metabolic rate due to reduced lean body mass. Preserving muscle is critical for lowering body fat.
While high-protein diets have shown benefits for weight loss and muscle maintenance, little research has explored how they affect women with NWO specifically.
How the Study Was Designed
Researchers conducted a 12-week double-blind randomised controlled trial to assess the impact of a high-protein diet on body composition and appetite in women with NWO.
Participants were women aged 30–60 with a BMI of 18.5–25 and body fat over 30%. Exclusion criteria included smoking, caffeine intake above 250 mg/day, chronic disease, pregnancy, and current use of protein supplements or high-protein diets.
Fifty women were randomly assigned to either a high-protein (HP) diet group consuming 25% of energy from protein or a standard-protein (SP) group consuming 15% of energy from protein. Both diets were eucaloric.
Body weight, fat mass, lean mass, waist circumference, and appetite were measured at baseline and 12 weeks.
What the Researchers Found
After accounting for dropouts and non-adherence, results were analysed from 24 HP participants and 23 SP participants.
- Lean body mass increased significantly in the HP group, with no major changes in the SP group.
- The HP group also showed lower fat mass, body fat percentage, and waist circumference.
- Neither group experienced significant changes in overall body weight or appetite.
Key Takeaways
The researchers concluded that a 12-week high-protein diet significantly improved body composition in women with NWO, even though it did not lead to overall weight loss.
However, limitations included the methods used to assess appetite and the lack of urine samples to confirm dietary compliance.
Because the study focused on a narrow age range and excluded many common conditions, further research is needed to create broader conclusions about protein and NWO.
