Why is it so easy to re­gain weight?

Healthy Food Guide (Australia) - - CONTENTS - Dr Tim Crowe is an Ad­vanced Ac­cred­ited Prac­tis­ing Di­eti­tian and nu­tri­tion re­search sci­en­tist. You can con­nect with him at think­ingnu­tri­

One of the most com­mon ex­pla­na­tions given for weight re­gain is a drop in our me­tab­o­lism. The idea has merit, but only re­veals part of the pic­ture. Mea­sur­ing changes in me­tab­o­lism is easy com­pared with get­ting an ac­cu­rate fix on how much food a per­son is con­sum­ing, as our eat­ing habits can change from day to day. Track­ing what and how much a per­son eats in the free-liv­ing world has proven a tough nut for sci­en­tists to crack.

Diet vs pills

A new way of look­ing at changes in eat­ing pat­terns af­ter weight loss was needed, and a novel way to do this arose from a clin­i­cal trial with a new drug for treat­ing di­a­betes. The drug, called canagliflozin, works by mak­ing the kid­neys ex­crete ex­cess glu­cose, which re­sults in lower blood-sugar lev­els.

And weight loss turned out to be a favourable side ef­fect.

In the trial, 153 peo­ple with type 2 di­a­betes took the drug for a year, while a com­par­i­son group of 89 peo­ple took a placebo pill. Both groups lost weight, but it was around 3kg in the drug-treat­ment group and just 1kg in the placebo group.

The sur­pris­ing re­sults

The slightly higher weight loss among those tak­ing the drug was not sur­pris­ing — the real mys­tery was why this group didn’t lose more weight.

Lab tests es­ti­mated the amount of en­ergy lost in the urine from ex­creted glu­cose was roughly 1500 kilo­joules (360cal) per day. That’s a lot of kilo­joules be­ing ex­creted by the body — so why did weight loss plateau?

To ex­plain the plateau, the re­search team bur­rowed into math­e­mat­i­cal mod­els of how body weight and en­ergy in­take are re­lated, and the an­swer they came up with was, quite sim­ply, ‘ap­petite’.

Driven by hunger

The prob­lem was, peo­ple in the drug-treat­ment group were hun­grier and this drove them to eat around 420 kilo­joules (100cal) ex­tra each day for ev­ery kilo­gram of weight they shed. In fact, the more weight they lost, the more they com­pen­sated by eat­ing. This surge in ap­petite that drives weight re­gain is three times stronger than the ef­fect of a slower me­tab­o­lism. Add the two to­gether and it ap­pears al­most in­evitable that, for most peo­ple, the weight will creep back on.

Mak­ing sense of it all

The re­al­ity is, re­gain­ing weight has lit­tle to do with poor self-con­trol. Our bod­ies are primed to fight against weight loss. We can ig­nore hunger cues for a while, but they will per­sist longer than our willpower. A bet­ter ap­proach is to take the fo­cus off ‘the best way to lose weight’ and, in­stead, look for pos­i­tive life­style changes which em­pha­sise a healthy re­la­tion­ship with food and, gen­er­ally, health­ier eat­ing habits that we can main­tain for life.

80% of peo­ple who lose weight put it back on over time

Sci­en­tists have dis­cov­ered why we are so hun­gry when we are on a diet

Our bod­ies are primed to fight against weight loss, by prompt­ing us to eat more

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