Protein intake and weight gain
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Protein Intake and Weight Gain: Key Findings
Total Protein Intake and Long-Term Weight Gain
Multiple large-scale studies in adults have found that higher total protein intake, especially from animal sources, is associated with greater long-term weight gain. This effect is most pronounced when protein replaces carbohydrates in the diet, and is particularly linked to protein from red and processed meats and poultry, rather than fish or dairy. In contrast, plant protein intake does not show a clear association with weight gain in these studies 13.
Animal vs. Plant Protein and Weight Gain
Evidence consistently points to animal protein—especially from meat and dairy—as being more strongly associated with increased body mass index (BMI) and weight gain, both in adults and children. Plant protein, on the other hand, does not show the same relationship with weight gain or obesity risk 1346. Some studies suggest that replacing animal protein with plant protein or carbohydrates may help reduce the risk of weight gain .
Protein Intake and Weight Gain in Children
In children, higher total protein intake, particularly from animal sources, is probably linked to higher BMI and increased risk of overweight or obesity later in childhood. This relationship is especially strong when high protein intake occurs in early childhood (up to 18 months), but may also extend into the second year of life. However, the evidence is less clear regarding the impact of protein intake after infancy, and more research is needed to determine safe upper limits 456.
Protein Intake and Weight Maintenance After Weight Loss
Some research suggests that a higher protein intake can help with weight maintenance after weight loss by increasing satiety and reducing the likelihood of regaining lost weight. In these cases, a modest increase in protein intake (e.g., from 15% to 18% of energy) was associated with less weight regain, mostly in the form of fat-free mass, and greater feelings of fullness 78.
Protein Intake in Special Populations
For very-low-birth-weight preterm infants, higher protein intake (between 3.5 and 4.0 g/kg/day) is linked to improved weight gain and developmental outcomes, but not necessarily to increased fat mass or obesity risk. The evidence in this group is specific to growth and development rather than long-term weight gain .
Interactions with Carbohydrate Quality
The impact of protein intake on weight gain can depend on what macronutrient it replaces. When protein replaces high-glycemic-load carbohydrates, the effect on weight gain may be less pronounced, and in some cases, certain protein foods (like yogurt, nuts, and seafood) are associated with relative weight loss or stability .
Conclusion
Overall, higher total and animal protein intake is associated with increased weight gain and higher BMI in both adults and children, especially when protein replaces carbohydrates in the diet. Plant protein does not show the same effect. However, higher protein intake may help with weight maintenance after weight loss in adults. In infants and young children, excessive protein intake—especially from animal sources—should be avoided to reduce the risk of later obesity. The relationship between protein intake and weight gain is complex and can depend on the source of protein, the age group, and the overall dietary context.
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