When people say that eating fat can make you gain weight, it is true IF you eat a lot of carbs with your fat.

This study was done to show the effects of increasing fat intake. It showed that people eating a 37% fat, 48% carb, 15% protein diet were less likely to gain weight than on a 50% fat, 35% carb, 15% protein diet. Lean men who exercised could take on the extra fat, but obese people showed possible insulin resistance meaning that the extra fat would be stored instead of used for fuel.

These diets if the total calorie intake was 2,239 per day had only 85 g protein. The subjects increased their fat intake from 91 g per day to 124 g per day. However, and this is the point, carbs only dropped from 270 g per day to 196 g per day. In other words, when eating that many carbs and increasing fat intake, you "gain" weight from the extra fat due to the insulin levels from the carbs.

My conclusion: Therefore studies showing that fat makes you gain weight are only valid if the carb level is left quite high.

Side note: This means "cheating" on your low carb diet can make you store fat!

Actual study:

American Journal of Clinical Nutrition, Vol. 71, No. 2, 450-457, February 2000
© 2000 American Society for Clinical Nutrition

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Original Research Communications

Fat and carbohydrate balances during adaptation to a high-fat diet1,2,3
Steven R Smith, Lilian de Jonge, Jeffery J Zachwieja, Heli Roy, Tuong Nguyen, Jennifer C Rood, Marlene M Windhauser and George A Bray
1 From the Pennington Biomedical Research Center, Baton Rouge, LA.

2 Supported by US Department of Agriculture grant 96034323-3031.


3 Address reprint requests to SR Smith, Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA 70808. E-mail: smithsr~mhs.pbrc.edu.




ABSTRACT
TOP
ABSTRACT
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION
REFERENCES


Background: Dietary fat contents are highly variable. Failure to compensate for the positive fat balance that occurs during the shift to a high-fat, low-carbohydrate diet by increasing energy expenditure or by decreasing food intake may result in the gain of fat mass.

Objective: The objective of this study was to investigate the time course of fat oxidation during adaptation to an isoenergetic high-fat, low-carbohydrate diet.

Design: After a 5-d control diet, dietary fat was increased from 37% of energy to 50% of energy for 4 d in 6 healthy, young lean men. Respiratory quotient and substrate macronutrient oxidation and balance were measured in a respiratory chamber. Fasting concentrations of insulin, glucose, and triacylglycerol; maximal oxygen consumption (O2max) during treadmill exercise; and free-living energy expenditure were determined. Body fat was measured by dual-energy X-ray absorptiometry and visceral adipose tissue by computerized tomography.

Results: Compared with the baseline diet, the high-fat, low-carbohydrate diet resulted in positive fat and protein balances and a negative carbohydrate balance. Insulin concentration and the postabsorptive respiratory quotient were positively correlated with the fat balance during the high-fat, low-carbohydrate diet, whereas O2max during treadmill exercise was negatively related to fat balance. With use of stepwise regression, O2max was the best predictor of fat balance. There was a negative correlation between fat balance and carbohydrate balance (r2 = 0.88).

Conclusion: Both baseline insulin concentration and O2max during treadmill exercise predict fat balance during the shift to a high-fat diet under isoenergetic conditions