WHICH WEIGHT LOSS DIET HELPS YOU TO LOSE WEIGHT AND LIVE LONGER?
New
year’s resolutions often include promises to lose weight. While
increasing physical activity is commonly part of the equation, for most
people, the burden of weight loss reduction focuses on the “diet”. The
problem is, which diet? Around 2,500 new “diet” books are published each
year – all proclaiming that their way is the only way to lose weight
and keep it off. As there are only three major nutrients – fat,
carbohydrate and protein – these “diets” typically manipulate (increase
or decrease) one or two of these macronutrients to achieve the desired
result. We only have to think about which diets have been popular over
the past 50 years or so to understand what is going on: low-carb diets
were fashionable in the 1970s; low-fat diets dominated the 80s and 90s;
now “low carb” has made a comeback. Food is fad when it comes to
“diets”.
But there are some good sound facts about
“diets”. Over the past 50 years, nutrition scientists have carried out
numerous randomized controlled trials investigating the effects of
various weight-loss diets on body weight and mortality (yes, death) and
the findings of these studies give us enough data to summarize their
effects using systematic review and meta-analysis statistical
techniques.
The most recent analysis looked at
long-term studies (greater than one year) of adults with a BMI greater
than 30kg/m2 in people from a European background and BMI greater than
25kg/m2 in people from other backgrounds including Asia and India. This
meta-analysis clearly shows there is level 1 evidence that low-fat diets
in combination with physical activity help people lose weight.
The
researchers found 54 trials involving 30,206 people who were followed
for up to 12 years. All but one of the trials included weight-loss
interventions that were low fat (less than 30% of energy from fat), and
most were also low in saturated fat. One study included the
Mediterranean diet and one was very low carb (less than 50 grams of
carb-containing foods a day). Most of the interventions included
exercise advice or an exercise program.
After one year,
the average weight reduction was 3.42kg (7.5 lb); at 2 years it was
2.51kg (5.5 lb); and at 3 years it was 2.56kg (5.6 lb). It may not sound
like a lot of weight, but these results are all statistically
significant and equivalent to each person losing and keeping off at
least five (500g/1.1lb) tubs of margarine or butter. This amount of
weight loss was also enough to have some significant effects on the risk
of premature death – a nearly 20% reduction in fact, or 6 lives saved
per 1000 people.
We are the first to agree that
one-size does not fit all when it comes to dietary patterns. But it is
important to note that at this point in time, there is not equivalent
level 1 evidence for the efficacy of long-term use of low-carb diets.
Read more:
- Effects of weight loss interventions for adults who are obese on mortality, cardiovascular disease, and cancer: systematic review and meta-analysis
- Effect of diet and exercise, alone or combined, on weight and body composition in overweight-to-obese post-menopausal women
- A High-Carbohydrate, High-Fiber, Low-Fat Diet Results in Weight Loss among Adults at High Risk of Type 2 Diabetes – I will cover this study in a future issue of GI News.
Alan Barclay, PhD is a consultant dietitian. He worked for Diabetes Australia (NSW) from 1998–2014 . He is author/co-author of more than 30 scientific publications, and author/co-author of The good Carbs Cookbook (Murdoch Books), Reversing Diabetes (Murdoch Books), The Low GI Diet: Managing Type 2 Diabetes (Hachette Australia) and The Ultimate Guide to Sugars and Sweeteners (The Experiment, New York).
