Fructose causes obesity by causing leptin resistance says Robert Lustig, MD

Lustig Theory of Obesity : Fructose causes insulin resistance which cause leptin resistance

Lustig’s slide show contains 109 slides, however, the four (4) slides shown below summarizes his theory of obesity.

In summary, Lustig suggests obesity is the result of too much fructose which causes elevated insulin levels (hyperinsulinemia), which causes insulin resistance, which causes leptin resistance.

He notes that when leptin levels are low as a result of not enough leptin, or when there is leptin resistance, which can be caused by too much insulin that can be caused by too much fructose, this produces a “starvation response”, reducing metabolism and increasing appetite, leading to weight gain and obesity.

He notes that:

• Leptin levels are determined by fat stores.
• Leptin tells your brain how thin you are, NOT how fat you are.
• The brain perceives a leptin deficiency as a state of starvation.
• A leptin deficiency decreases energy expenditure.
• A leptin deficiency causes thyroid levels to decline (reducing metabolism).
• Producing more leptin (leptin repletion) corrects this.
• Calorie restriction causes leptin levels to fall, and increases appetite.
• Obese people have elevated leptin levels, but are leptin resistant.
• If we could fix the leptin resistance, there would not be obesity.

Lustig suggests that insulin blocks leptin

Lustig also suggests that insulin blocks leptin.

His argument for this is as follows:

• Insulin allows humans to gain weight when necessary, such as during puberty and pregnancy.
• Insulin does this by causing leptin resistance.
• He asks, “Doesn’t it make sense that the same hormone (insulin) that promotes fat storage, also inhibits leptin so that energy can be stored?”

Fructose causes insulin resistance which causes leptin resistance

He states that:

• Fructose induces insulin resistance which induces leptin resistance.

He says from an evolutionary sense (Darwinian sense) that:

• There was seasonal insulin resistance.
• Fructose was available at harvest for 1-2 months per year.
• This was followed by 4-5 months of winter when no food was available.
• If leptin worked all the time, you could not store energy (fat).
• There is a selective advantage of induding this seasonal insulin resistance by gorging on fruit when it was available.
• However, fructose is not available about all the time, and is consumed in unlimited amounts, and is unopposed by fiber naturally present in foods.

Lustig’s summary of how fructose causes obesity by causing insulin resistance and leptin resistance

In summary, Lustig notes that:

• Obesity means leptin resistance, or “brain starvation”.
• The starvation response causes people to regain lost weight.
• Energy expenditure and the quality of life are the same thing.
• Defects in insulin signaling promote leptin resistance.
• Fructose cause insulin resistance in the liver, leading to weight gain and continued consumption.
• Our environment is insulinogenic; we have to “get the insulin down”.

About Robert Lustig, MD

Robert H. Lustig, M.D. is a Professor of Clinical Pediatrics, in the Division of Endocrinology, and Director of the Weight Assessment for Teen and Child Health (WATCH) Program at the University of California, San Francisco.

More info about Dr. Lustig is posted here.

Robert Lustig, MD
University of California, San Francisco
513 Parnassus Avenue
San Francisco, CA 94143-0434
Campus Box 0434, S-679

415-502-8672 phone
415-476-8214 fax
Email: .(JavaScript must be enabled to view this email address)

Lustig’s slide show is posted here

Lustig’s slide show titled “The Trouble with Fructose: A Darwinian Perspective” which contains 109 slides is posted here.

The following four (4) slides summarizes his theory of the cause of obesity.

Articles on the same subject can be found here:

• Doctor - Robert Lustig, MD

• Fructose

• High-Fructose Corn Syrup

• Insulin

• Insulin sensitivity

• Leptin