Calorie restriction

When reducing caloric intake, there is a reduction in basal metabolic rate, and there also is reduction is spontaneous physical activity. If the calorie restriction is severe enough, the bodies go into starvation mode, which will counteract any fat loss efforts [1,2]. 

Specific food restriction

A diet usually has an explicit (or implicit) list of foods that it recommends. Eating specific foods can have a more psychological impact than calorie restriction per see, especially if you don't like the foods that are prescribed in your diet plan. 

The different types of "cheating"

Now back to the issue of cheating. Looking at calorie restriction and specific food restriction separately, you see that you can cheat in three different ways:

- eating more calories from the same "dieting foods"      (quantitative cheating) 

- eating non-dieting "forbidden" foods, but still within your daily calorie allotment     (qualitative cheating)  

- eating non-dieting "forbidden" foods AND exceeding your daily calorie allotment    (double whammy cheating!)      


Dieting cheating is not necessarily yo-yo dieting

Before we continue I want to make clear that this discussion on diet cheating should not be confused with yo-yo dieting (also called weight cycling; when one is repeatedly losing and regaining weight). Yo-yo dieting definitely can have detrimental effects, especially psychologically [3,4]. 


Possible benefits and risk with cheating on a diet?

Allowing some diet flexibility on weekends, holidays, and vacations might reduce boredom, which is a known contributor to dieting lapses [5], and be more realistic in a long-term perspective. However, flexibility might also increase exposure to high-risk situations, and the chance for loss of control. This is especially true among people with addictive personalities [6]. 


What does research show?

While it is well documented that holidays are associated with fat gain [7-9], it wasn't until recently that studies started to investigate the influence of weekend eating patterns on short- and long-term body fat mass. The first study on weekend eating patterns was done on National Weight Control Registry subjects, who had successfully maintained a weight loss of at least 13.6 kg for 8 years [10]. The purpose of the study was to examine whether maintaining the same diet regimen across the week and year promotes weight control or if dieting more strictly on weekdays and/or non-holidays is more conducive to long-term maintenance.

Participants who reported greater dieting consistency (i.e. those who cheated less) were more likely to maintain their weight within 2.3 kg during the subsequent year, whereas participants with lower dieting consistency scores were more likely to regain weight during the subsequent year [10]. A more recent study, where subjects consumed on average 236 calories more on weekend days confirmed that weekend dietary indulgences contribute to weight gain or cessation of weight loss [11].

It has also been documented that as the duration of a diet increases - that is, the longer you are on a diet - a shift in the balance between effort and pleasure of weight maintenance may occur [12]. This  makes it easier to stick to the diet, and thereby increases the likelihood of continued fat loss maintenance 12. This is supported by findings showing that repeated exposure trains flavor preference 13. In other words, a strong correlation exists between a person’s customary intake of a flavor (or lack of flavor) and his preference for that flavor (or lack of that flavor).


Bottom Line

Whether cheating on a diet  will cause you any harm or good depends on your personal inclinations, and the reasons for the cheating.  

From a biological perspective, I believe quantitative cheating, when you eat more calories from the same "dieting foods", can be a good thing, since it can prevent lowering your resting metabolic rate and drops in spontaneous physical activity. 

When it comes to the other types of  cheating, the consequences are more of a psychological origin. If you have an addictive personality, do not even think about cheating. Remember, the best cure for any addiction is complete abstinence. 

If you don't have an addictive personality, but have a lot of fat to shed, it is ok for you to engage in quantitative or qualitative cheating once in a while, when you eat non-dieting "forbidden" foods, but still within your daily calorie allotment. 

If you don't have that much fat to drop and are just dieting to get in a little better shape, you can indulge in double whammy cheating, ie eating non-dieting "forbidden" foods AND exceeding your daily calorie allotment. Just don't go too much overboard; your body and mind will still take note of what you're doing. 

In any case, the reason for you to cheat on a diet should be that it helps you to stay on track in the long run. Not because other people coerce you to eat bad stuff or are trying to make you believe that you "have to" cheat on your diet to get good results. That's nonsense you often hear from folks who don't have the willpower and discipline themselves. It has actually been shown that friends have an even larger impact on a person's risk of obesity than do genes [14]!  So don't fall for the peer-pressure and never engage in risky behaviors just because your friends do! 

You know yourself better than anybody else. If you know you easily lose control, then cheating on a diet is not for you and you should put your foot down and stick to your guns. On the other hand, if a cheat meal once in while helps you to stick to your diet in the long run, then go ahead. Getting in shape is a long-term project, so you want to find strategies that will help you along way.



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